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You can avoid failure in the SAP central services – that is, ASCS for ABAP or SCS for Java – by using the methods described below.


Message Service

The message service is the system communications hub, acting as a “name server” to return the required service on request. It distributes the cluster events and enables service-to-service communication. It also provides information for load balancing over the SAP Web dispatcher.

If the message service fails, this disturbs the communication between the cluster nodes. The only way to protect the message service from failure is to use switchover software. After the switchover software restarts the message service, cluster communication continues.

Enqueue Service

The enqueue service provides a central lock table for logical locks on database objects to protect these objects from unsynchronized writes by the AS Java programs.

When the enqueue service fails, all open transactions have to be rolled back to prevent inconsistencies. If the enqueue service fails, the applications with requested locks get an exception that has to be handled by the application.

You can solve this problem in the following ways:

  • Basic solution – switchover software for failover protection

    You need to at least protect the enqueue service with switchover software. This makes sure that the enqueue service can be restarted and is available again. However, even with switchover software, transactions open at the time of failure have to be rolled back.

  • Advanced solution – standalone enqueue replication service for protection of the internal system state

    You can also use the standalone enqueue replication service, which maintains a replica of the lock table. This replica can be used in the event of failover to restore the lock table without the need to roll back transactions.

    Note that there might be restrictions for the product availability of the standalone enqueue replication service.

Recommendation Recommendation

For full protection of your enqueue service, we recommend you to use both the solutions described above.

End of the recommendation.