## 1 SAP HANA System Replication
The SAP HANA System Replication guide is the entry point for all information related to SAP HANA system replication.
## Why should I use SAP HANA system replication?
SAP HANA system replication is a mechanism ensuring the high availability of your SAP HANA system. System replication is SAP's recommended configuration for addressing SAP HANA outage reduction due to planned maintenance, faults, and disasters. It supports a recovery point objective (RPO) of 0 seconds and a recovery time objective (RTO) measured in minutes.
## What can I learn about SAP HANA system replication in this guide?
Before configuring your system replication landscape, it's important to learn about basic concepts.
You will have to take decisions related to the used operation and replication modes. The selected operation mode determines what types of data packages are sent to the secondary system. The operation mode determines also which technique (data retention or log retention) is used to achieve a resync whenever system replication is out of sync. The network connection between the primary and the secondary systems is also important, because it impacts the overall performance of the systems involved in a system replication landscape. Finally, in system replication landscapes you can run also other systems (for example, DEV, QA systems, or even productive systems) on the secondary system's hardware while the primary system is in production. For information on these aspects, see SAP HANA System Replication: Basic Concepts .
After checking all the necessary prerequisites for configuring system replication, you can use the SAP HANA cockpit, the SAP HANA studio, or the hdbnsutil command line tool to configure system replication. At this point, it's also useful to know how to initialize the secondary system, how to change the chosen operation or replication mode, or how to add or remove hosts. You can enable the full sync option in a synchronous system replication to reach a true RPO=0. For information on these aspects, see SAP HANA System Replication: Configuration . This chapter also provides an overview of the configuration parameters, a command line reference, as well as information about SAP HANA tenant database systems in a system replication configuration, and the system replication setup for XS advanced.
Learn next how to perform a takeover and a failback for planned or unplanned downtimes of the primary system. You can perform a standard takeover, a takeover with handshake, or an invisible takeover. For information, see SAP HANA System Replication: Takeover and Failback .
To quickly access again data, which was deleted in the original system, you can prepare your system replication landscape for secondary time travel. Secondary time travel allows you to start the secondary system or the log replay at a previous point in time. For information, see SAP HANA System Replication: Secondary Time Travel .
To support read access on the secondary system, you can configure an Active/Active (read enabled) system replication. Active/Active (read enabled) reduces the load on the primary system, but does not double the
capacity; it simply extends read capabilities. In an Active/Active (read enabled) system replication configuration, the SQL ports on the secondary system are open for read access. This makes it possible to use the secondary system for read-intense tasks and to have a better balance of workloads improving the overall performance of the SAP HANA database. For more information about Active/Active (read enabled), see SAP HANA System Replication with Active/Active (Read Enabled) .
Besides the standard setup, in which a primary system ships all the data to the secondary system, you can also configure a multitier or a multitarget system replication. In a multititer system replication, a tier 2 system replication setup can be used as the source for adding further tiers in a chain. In a multitarget system replication, the primary system can replicate data changes to more than one secondary system. To learn how to configure the different setups and how to handle in different disaster recovery scenarios, see SAP HANA System Replication Setups .
There are multiple ways to monitor system replication and to verify if the primary and secondary systems are in sync and are running correctly:
- Alerts on the primary and secondary systems warn you of potential problems.
- To ensure rapid takeover in the event of planned or unplanned downtime, you can check the status of the replication between the primary and the secondary systems.
- You can monitor system replication using the SAP HANA cockpit, the SAP HANA studio, the hdbnsutil command line tool, or SQL queries.
For more information, see SAP HANA System Replication: Operation and Maintenance . This chapter also includes information about the network connection, how to copy or move tenants in a system replication configuration, or how to use SAP HANA system replication to update your SAP HANA systems.
Troubleshoot System Replication describes how to analyze, avoid, and solve problems related to system replication.
Communication between systems in a system replication scenario is always authenticated. In addition, it is possible to secure internal network communication between primary and secondary systems using TLS/SSL. For more information, see Security Aspects for SAP HANA System Replication .
Finally, use the SQL and System View Reference chapter in this guide to have a look at the system views relevant for system replication (for example, M\_SERVICE\_REPLICATION, M\_SYSTEM\_REPLICATION).
## Related Information
| SAP HANASystem Replication: Basic Concepts [page 8]                     |
|-------------------------------------------------------------------------|
| SAP HANASystem Replication: Configuration [page 34]                     |
| SAP HANASystem Replication: Takeover and Failback [page 85]             |
| Secondary Time Travel [page 107]                                        |
| SAP HANASystem Replication with Active/Active (Read Enabled) [page 113] |
| SAP HANASystem Replication Setups [page 128]                            |
| SAP HANASystem Replication: Operation and Maintenance [page 147]        |
| Troubleshoot System Replication [page 209]                              |
| Security Aspects for SAP HANASystem Replication [page 251]              |
| SQL and System View Reference [page 269]                                |