Performing a Forced System Replication Takeover
If your primary system is not available, due to a disaster or planned downtime for example, and you have decided to fail over to the secondary system, you can perform a forced system replication takeover on your secondary node.
Prerequisites
-
You have permission Service(ForcedPrepare,ForcedUnPrepare,ForcedStart,ForcedStop).
For more information, see Standard Permissions.
-
You have assigned the roles and groups required to perform the operation.
For more information, see Standard Roles and Groups.
-
You have set up and configured system replication.
For more information, see Setting Up System Replication.
-
SAP Host Agent 7.20 SP 191 or above
-
You have selected the Show Advanced Shutdown Options when Stopping Operations checkbox during engine configuration.
For more information, see Configuring Advanced Operation Settings.
-
The secondary system is independently up and running.
-
You have assigned the client connect address for the automatic IP redirect during system replication takeover.
For more information, see Instance Properties.
Context
A forced system replication takeover implements the SAP HANA hdbnsutil -sr_takeover operation. Use the forced system replication takeover operation only in case of emergency operations with support of a cluster for the client connect IPs or within a custom process, where other steps ensure the avoidances of a network split, a so called“split brain” as well as the client connectivity.
-
If site B (secondary tier) is taking over, the operation will not make any attempt to stop or change the state of site A (primary tier). It depends on the data center infrastructure and the exception causing the takeover, how site A can be made unavailable for clients to avoid a "split brain."
-
You are responsible to only do a forced system replication takeover if all transactions executed on site A have been replicated to site B, and site A has been made unavailable for clients. For example, make sure the primary tier on site A is completely stopped or re-assign the virtual IP to the host assigned to site A.
-
Since multiple ways of backups are supported, do not start site A as primary tier in case there are possibilities for site A to share backups with site B. If and how backups are synced is in the responsibility of the administrators.
Procedure
Next Steps
-
Optional: Register the former primary system as the secondary system when it becomes available again.
For more information, see Registering a Secondary Tier for System Replication.
-
Optional: Execute the Failback.
For more information, see Performing a Failback.



