## 2.3 Performance and High Resource Utilization
By observing the general symptoms shown by the system such as poor performance, high memory usage, paging or column store unloads we can start to narrow down the possible causes as a first step in analyzing the issue.
## High Memory Consumption
You observe that the amount of memory allocated by the SAP HANA database is higher than expected. The following alerts indicate issues with high memory usage:
- Memory usage of name server (Alert 12)
- Total memory usage of Column Store tables (Alert 40)
- Memory usage of services (Alert 43)
- Memory usage of main storage of Column Store tables (Alert 45)
- Runtime dump files (Alert 46)
See the section Memory Problems for information on analyzing the root cause.
## Out-of-Memory Situations
You observe trace files or error messages indicating an Out-of-Memory (OOM) situation.
See the section Memory Problems for information on analyzing the root cause.
## Paging on Operating System Level
You observe that paging is reported on operating system level.
See the section Memory Problems for information on analyzing the root cause.
## Column Store Unloads
You observe unloads in the column store. The following alerts indicate issues with high memory usage:
- Column store unloads (Alert 55)
See the section Memory Problems for information on analyzing the root cause.
## Permanently Slow System
Issues with overall system performance can be caused by a number of very different root causes. Typical reasons for a slow system are resource shortages of CPU, memory, disk I/O and, for distributed systems, network performance.
Check Overview Monitoring and Administration Performance Monitor for either Memory , CPU or Disk Usage . If you see a constant high usage of memory or CPU, proceed with the linked sections Memory Problems or CPU Related Root Causes and Solutions respectively. I/O Related Root Causes and Solutions provides ways to check for disk I/O related problems. In case of network performance issues, have a look at the Monitor Network page accessible from the Monitoring group in the SAP HANA cockpit.
Note that operating system tools can also provide valuable information on disk I/O load. Basic network I/O data is included in the Load graph and in the m_SERVICE_NETWORK_IO system view, but standard network analysis tools can also be helpful to determine whether the network is the main bottleneck. If performance issues only appear sporadically, the problem may be related to other tasks running on the database at the same time.
These include not only maintenance related tasks such as savepoints (disk I/O, see I/O Related Root Causes and Solutions ) or remote replication (network I/O), but also SQL statements dispatched by other users, which can block a lot of resources. In the case of memory, this can lead to unloads of tables, which affects future SQL statements, when a table has to be reloaded into memory. In this case, see Memory Problems as well. Another reason for poor performance, which in many cases cannot be detected by the SAP HANA instance itself, are other processes running on the same host that are not related to SAP HANA. You can use the operating system tools to check for such processes. Note that SAP only supports production systems running on validated hardware.
## Slow Individual SQL Statements or with Increasingly Long Runtimes
Issues with the performance of a particular statement can be caused by a number of very different root causes. In principle, a statement can trigger all the resource problems that also lead to an overall slowdown of the system, so most of the previous information also applies to statement performance. In addition, statement performance can suffer from transactional problems, that is, blocked transactions. Blocked transactions can be checked in the Threads tile or on the Blocked Transactions page accessible from the Monitoring group. For troubleshooting, proceed with Transaction Problems .
If the runtime of a statement increases steadily over time, there could be an issue with the delta merge operation. Alerts should be issued for most problems occurring with the delta merge, but since they depend on configurable thresholds, this is not always the case. For troubleshooting, proceed with Delta Merge . If you have none of the above problems, but the statement is still too slow, a detailed Statement Performance Analysis might reveal ways to optimize the statement. However, some queries are inherently complex and require a lot of computational resources and time.
## Related Information
Memory Problems [page 65]
CPU Related Root Causes and Solutions [page 82] Disk Related Root Causes and Solutions [page 106] I/O Related Root Causes and Solutions [page 114] m_SERVICE_NETWORK_IO Transactional Problems [page 167] Delta Merge [page 129] Statement Performance Analysis [page 180]