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Basic Failure Classification

When thinking about fault-tolerance, you can look at failure in the following ways:

  • Service failure

    This section discusses failure of the SAP system services in detail:

    • How to detect failure

    • The effects of failure

    • How to recover from failure

  • SAP central services

Potential Single Points of Failure

The database, enqueue, and message services in a standard SAP system cannot be made redundant by configuring multiple instances of them on different host machines: this means that they are potential single points of failure (SPOFs). The remaining services (that is, dialog, update, background, gateway, and spool) can all be configured redundantly (in other words, on multiple host machines) to provide improved availability.

In a high availability SAP system, you can protect vulnerable services, such as the enqueue, message, and database services by using, for example, cluster environments with switchover solutions. For more information, see:

Failure Recovery

Finally, see Failure Recovery for more information on how SAP systems recover following failure:

  • Automatic recovery of SAP processes

  • Logon load balancing (prevents users logging on to a dialog host that has failed)