eG Monitoring
 

Measures reported by HanaRepStatTest

SAP HANA offers different kinds of high availability mechanisms, supporting a broad range of recovery scenarios from various faults. There are three basic scenarios:

    Host Auto-Failover: One (or more) standby nodes are added to an SAP HANA system and configured to work in standby mode. (SAP HANA scale-out).

    Storage Replication: The storage itself replicates all data to another location (this solution is provided by hardware partners). Disks are mirrored without a control process from the SAP HANA system.

    System Replication: SAP HANA replicates all data to a secondary SAP HANA system (standard SAP HANA feature). Data is constantly pre-loaded on the secondary system to minimize the recovery time objective (RTO)

SAP HANA system replication ships all data to a secondary system located at another site. Once SAP HANA system replication is enabled, each server process on the secondary system establishes a connection with its primary counterpart and requests a snapshot of the data. Then, all logged changes in the primary system are replicated continuously. Each persisted redo log in the primary system is sent to the secondary. A transaction in the primary system is not committed before the redo logs are replicated. While the system replication is running, the secondary system, which is configured identically to the primary, will be on standby until a takeover takes place. The takeover process is the name for the task of switching your active system from the current primary system onto the secondary system. Once the takeover command runs, the former secondary system becomes the new primary system.

In a high availability environment, the secondary system should always be in sync with the primary system. For this, the system replication should always be running so that the secondary system is replicated with the data from the primary system. If the replication fails even for a brief period, the secondary system will not have the updated data leading to outdated data. To avoid this, it is essential to monitor the replication status of the primary system. The Hana Replication Status test helps administrators in this regard!

This test monitors the current replication status of the target database server and also report whether/not the secondary server is active or not in a high availability setup. Using this test, administrators can determine if the system replication is active on the target database server or is error prone.

Outputs of the test: One set of results for the target SAP HANA database server being monitored.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
ReplicationStatus Indicates the current replication status of the target database server.  

The numeric values that correspond to the measure values are as follows:

Measure value Numeric Value
Error 0
Unknown 1
Initializing 2
Syncing 3
Active 4

Note:

By default, this measure reports the Measure Values in the table above to indicate whether/not the secondary server is active. However, in the graph of this measure, the same is represented using the numeric equivalents only.

Is_secondary_active Indicates whether/not the secondary server is active.  

If the secondary server is active, this measure will report the value Yes. If it is not active, then this measure will report the value No. The numeric values that correspond to these measure values are as follows:

Measure value Numeric Value
Yes 1
No 0

Note:

By default, this measure reports the Measure Values in the table above to indicate whether/not the secondary server is active. However, in the graph of this measure, the same is represented using the numeric equivalents only.