How SAP Failover Works with SAP Replication Server

To configure SAP Failover from SAP Replication Server to SAP ASE, the SAP ASE must be configured to allow connection failover.

When SAP ASE servers are in failover companion mode and the primary companion fails, the secondary companion takes over the workload. Incomplete transactions or operations that require updates to the RSSD fail. SAP Replication Server retries existing connections, but new connections are failed over.

For Data Server Interface (DSI) connections, the DSI retries failed transactions after a brief sleep.

For RSSD connections, user commands that are executed during failover do not succeed. Internal operations such as, updates to locator and disk segment should not fail. Replication of RSSD objects should be covered by the DSI.

Asynchronous commands (for example, subscription, routing, and standby commands) may be rejected or encounter errors and require recovery if the commands have been accepted but not completed. For example, a create subscription command may have been accepted, but the subscription may still be being created.

Note: Failover support is not a substitute for warm standby. While warm standby keeps a copy of a database, Failover support accesses the same database from a different machine. Failover support works the same for connections from SAP Replication Server to warm standby databases.