## 3.8 SAP HANA System Replication Configuration Parameters
Several configuration parameters are available for configuring SAP HANA system replication between the primary and secondary system.
The system replication parameters are defined in the [system\_replication] section of the global.ini file and have the default values shown below. The System column defines whether the parameter can be set on the primary, the secondary, or both.
##  Note
preload\_column\_tables uses the Boolean keywords "true" or "false". Numbers do not work in place of the keywords.
| Parameter   | datashipping_min_time_interval   |
|-------------|----------------------------------|
| Type        | int                              |
| Unit        | seconds                          |
| Default     | 600 (10 min)                     |
| System      | Secondary                        |
| Parameter   | datashipping_min_time_interval                                                                                                                                                                                                                                                                                                                                      |
|-------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | Minimum time interval between two data shipping requests from the secondary system. If datashipping_logsize_threshold (see next parameter) is reached first, the data shipping re­ quest will be sent before the time interval is elapsed when the log size threshold is reached.                                                                                    |
| Parameter   | datashipping_logsize_threshold                                                                                                                                                                                                                                                                                                                                      |
| Type        | int                                                                                                                                                                                                                                                                                                                                                                 |
| Unit        | bytes                                                                                                                                                                                                                                                                                                                                                               |
| Default     | 5*1024*1024*1024 (5 GB)                                                                                                                                                                                                                                                                                                                                             |
| System      | Secondary                                                                                                                                                                                                                                                                                                                                                           |
| Description | Minimum amount of log shipped between two data shipping requests from the secondary system. If the time defined by datashipping_min_time_interval (see previous parameter) has passed before reaching this threshold, the data shipping request will be sent before this threshold is reached when the time interval has elapsed.                                   |
| Parameter   | preload_column_tables                                                                                                                                                                                                                                                                                                                                               |
| Type        | bool                                                                                                                                                                                                                                                                                                                                                                |
| Unit        | true/false                                                                                                                                                                                                                                                                                                                                                          |
| Default     | true                                                                                                                                                                                                                                                                                                                                                                |
| System      | Primary and Secondary                                                                                                                                                                                                                                                                                                                                               |
| Description | If activated column store tables are preloaded to the main part of memory. If set on the primary system, the loaded table information is collected and stored in the snapshot that is shipped. If set on thesecondary system, this information is evaluated and the tables are actually preloaded there according to the information received on the loaded tables. |
| Parameter   | datashipping_snapshot_max_retention_time                                                                                                                                                                                                                                                                                                                            |
| Type        | int                                                                                                                                                                                                                                                                                                                                                                 |
| Unit        | minutes                                                                                                                                                                                                                                                                                                                                                             |
| Default     | 300                                                                                                                                                                                                                                                                                                                                                                 |
| System      | Primary                                                                                                                                                                                                                                                                                                                                                             |
| Parameter   | datashipping_snapshot_max_retention_time                                                                                                                                                                                                                                                                                                                                                                                      |
|-------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | Maximum retention time (in minutes) of the last snapshot that has been completely shipped to the secon­ dary system.                                                                                                                                                                                                                                                                                                           |
| Parameter   | logshipping_timeout                                                                                                                                                                                                                                                                                                                                                                                                           |
| Type        | int                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Unit        | seconds                                                                                                                                                                                                                                                                                                                                                                                                                       |
| System      | Primary                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Description | Number of seconds the primary waits for the acknowledgment after sending a log buffer to the secondary system. If the primary does not receive the acknowledgment for a sent log buffer within the time defined by logshipping_timeout , it closes the connection to the secondary system in order to continue data processing. This is done to prevent the primary system from blocking transaction processing if there is a |
| Parameter   | logshipping_async_buffer_size                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Type        | int                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Unit        | bytes                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Default     | 67108864 (64MB)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| System      | Primary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Description | In asynchronous replication mode, the log writer copies the log buffers into an intermediate memory buffer first and continues processing. A separate thread reads log buffers from this memory buffer and sends them to the secondary system asynchronously over the network. This parameter determines how much log can be intermediately buffered. This buffer is especially useful in peak times when log is generated faster than it can be sent to the secondary system. If the buffer is large, it can handle peaks for a longer period of time. The behavior of buffer full situations can be controlled by the parameter logshipping_async_wait_on_buffer_full . The parameter can be changed online, but will become active the next time the secondary system recon­ nects. |
| Parameter   | logshipping_async_wait_on_buffer_full                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Type        | bool                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Unit        | true/false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Default     | true                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| System      | Primary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Parameter   | reconnect_time_interval                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Type        | int                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Unit        | seconds                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Default     | 30                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| System      | Secondary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Parameter   | reconnect_time_interval                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | If a secondary system is disconnected from the primary system because of network problems, the secon­ dary system tries to reconnect periodically after the time interval specified in this parameter has passed.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Parameter   | enable_full_sync                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Type        | bool                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Unit        | true/false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Default     | false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| System      | Primary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Description | If set, system replication operates in full sync mode when the SYNC replication mode is set. In full sync mode, transaction processing blocks when the secondary is currently not connected and newly created log buffers cannot be shipped to the secondary system. This behavior ensures that no transaction can be locally committed without shipping to the secondary system. For more information, see Full Sync Option for SAP HANASystem Replication .                                                                                                                                                                                                                                                                                                                         |
| Parameter   | enable_log_compression                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Type        | bool                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Unit        | true/false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Default     | false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| System      | Secondary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Description | If activated, log buffers will be compressed before sending them over the network to the secondary sys­ tem. The secondary system decompresses the log buffers it receives and then writes them to disk. If the network bandwidth is the bottleneck in the system replication setup, log buffer compression can improve log shipping performance because less data is being sent over the network. The drawback to sending a compressed log buffer to the secondary system is that it requires additional time and processing power for compression and decompression. This can result in worse log shipping per­ formance if turned on in a configuration with a fast network. The parameter has to be set on the secondary system. It can be changed online, but the secondary system |
| Parameter   | enable_data_compression                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Type        | bool                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Unit        | true/false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Default     | false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
Parameter enable\_data\_compression
| System      | Secondary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|-------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | If activated, data pages will be compressed before sending them over the network to the secondary sys­ tem. The secondary system decompresses the data pages it receives and then writes them to disk. If the network bandwidth is the bottleneck in the system replication setup, data compression can improve log shipping performance because less data is being sent over the network. The drawback to sending compressed data pages to the secondary system is that it requires additional time and processing power for compression and decompression. This can result in worse data shipping performance if turned on in a configuration with a fast network. The parameter has to be set on the secondary system. It can be changed online, but the secondary system has to re-connect to the primary system in order to activate the parameter change. |
| Parameter   | keep_old_style_alert                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Type        | bool                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Unit        | true/false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Default     | false                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| System      | Primary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Description | Before SPS 09 closed replication connections and configuration parameter mismatches were alerted with Alert 21. With SPS 09 two dedicated alerts have been introduced for both error situations. By default old style alert­ ing is still offered for backwards compatibility. When setting this parameter to false, the old behavior is turned off and only new alerts will be generated. For more information, see SAP HANASystem Replication Alerts .                                                                                                                                                                                                                                                                                                                                                                                                        |
| Parameter   | operation_mode                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Type        | enum                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Unit        | delta_datashipping/logreplay/logreplay_readaccess                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Default     | logreplay                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| System      | Secondary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Parameter   | operation_mode                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | Operation mode of the secondary site during replication. There are three different settings for this parameter: ● delta_datashipping System Replication uses data and log shipping for replication. Log buffers received by the secondary system are just saved to disk, savepoints after intermediate delta data shippings truncate the log. Col­ umntable merges are not executed on the secondary system, but merged tables on the primary sys­ tem are transported via delta data shippings to the secondary system. ● logreplay |
| Parameter   | enable_log_retention                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Type        | enum                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Unit        | auto/off/on                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Default     | auto                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| System      | Primary, Secondary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Parameter   | enable_log_retention                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | Enables or disables log retention on a system replication system. Log retention on the primary system is useful when the secondary should sync with the primary by re-shipping missing log after a network outage or downtime. If the missing log is not available anymore on the primary system, a data shipping is required (delta in operation mode delta_datashipping , full in all other operation modes). Log retention on the secondary system is needed to keep log for optimized re-sync during failback. |
| Parameter   | logshipping_max_retention_size                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Type        | int                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Unit        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Default     | MB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|             | 1048576 (1TB)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| System      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|             | Primary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Parameter   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|-------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | Sets the maximum amount of log that will be kept for syncing a secondary system. This value only has an effect if log retention is enabled. Two situations have to be distinguished here: If logshipping_max_retention_size has been set to a value other than 0, when no secondary is connected log segments are not reused even if they are truncated and backed up until the max size limit has been reached or the system runs into a log full situation. If the maximum size limit is reached or in log full situations, the segments that are only kept for syncing the                                                                                                                                                                                                    |
|             | because of too many log segments that are held for syncing the secondary system. With this setting, the primary keeps running with the drawback that the secondary cannot sync anymore. If logshipping_max_retention_size is configured to 0, log segments required for syncing the secondary are not reused and a log full results in a system standstill on the primary system until log writing                                                                                                                                                                                                                                                                                                                                                                               |
|             | can continue. This setting allows you to configure an upper limit up to which redo log segments are kept in RetainedFree state on the primary system before they are overwritten for syncing with a secondary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|             |  Note The default setting logshipping_max_retention_size = 1048576 (MB) of 1 TB means that 1 TB of size is configured for every service, which replicates data to a secondary system. That is, every service owning a persistence in form of data and log volume.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|             |  Example If the services nameserver, two indexservers (for example, two tenant databases) and an xsengine are running in your SAP HANAsystem, the total configured log retention size will be 4 TB (4 x 1 TB). With this setting it can happen that the disk full is reached before the RetainedFree marked log segments are overwritten. If you want to change the default value of 1 TB, you can do this in the global.ini. Another option is to set this parameter in the service ini files individually. For example, if the value is set in the global.ini of the system database, in the global.ini of a tenant database, and in the indexserver.ini of a tenant database, the indexserver.ini setting would win and will be taken for log retention of this indexserver. |
| Parameter   | datashipping_parallel_channels                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Type        | int                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Default     | 4                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| System      | Secondary                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Parameter   | datashipping_parallel_channels                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|-------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Description | The parameter defines the number of network channels used by full or delta datashipping. The actual number of channels for each shipping can be adjusted by the system to reduce overhead depending on the current amount of data to be shipped. Higher parallelism can be useful when large amount of data (above several GBat least) needs to be ship­ ped and the utilization of network bandwidth by single network stream is low. Please note that the overall bandwidth is still limited by the I/O bandwidth, because the data needs to be read from the primary sys­ tem. To deactivate the parameter, change the default to 0. |
## Related Information
Full Sync Option for SAP HANA System Replication [page 58] Operation Modes for SAP HANA System Replication [page 14] Log Retention and Multitarget System Replication [page 25] Change a System Property in SAP HANA Studio Log Retention [page 20]