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Patching Procedure
Applies to OS patching and Database Patching.Patching Procedure
If replicas are not fully synchronized, failover may cause data loss.
Confirm:
- All databases synchronized.
- No suspended data movement.
- No AG health warnings.
- Sufficient failover partners available.
Assumptions:
- Applications connect via the AG Listener
Only patch one replica at a time and wait for AG to resynchronise before continuing. Beware of MFSP.
Patch Async Secondary Replica(s) first.
Install OS updates.
Install SQL Server updates.Reboot (if required).
Confirm replica rejoins and synchronization resumes.
Patch Sync Secondary Replica(s)
Install OS updates.
Install SQL Server updates.Reboot (if required).
Confirm replica rejoins and synchronization resumes.
Perform Controlled Failover
ALTER AVAILABILITY GROUP [AG_NAME] FAILOVER;
Assuming synchronous commit and synchronized state, this gives a zero-data-loss failover.This must be executed from a secondary replicaPatch former Primary
Install SQL Server updates.Reboot (if required).
Confirm replica rejoins and synchronization resumes.
Perform Controlled Failover (only if you have to)
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