ABAP central services and enqueue replication server

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Read information about the policy definition of the ABAP central services and the closely related enqueue replication server. The mechanisms in the Java™ part (see Java central services and enqueue replication server) are similar to this one.

Figure 1 shows the lowest level in the group structure of the ABAP central services and enqueue replication server.

Figure 1. Lowest level in group structure of ABAP central services and enqueue replication server
Lowest level in group structure of ABAP central services and enqueue replication server

SAP<SID>AENQX of Figure 1 contains these resources:

  • The ASCS sapstartsrv process (SAP<SID>A_SRV), which must be active to start the ABAP SCS instance
  • The VIPA associated with the ABAP SCS instance (SAP<SID>ACV)
  • The ABAP sapstart process (SAP<SID>A_STA [subsystem name SAP<SID>AST]), which is the parent process of:
    • ABAP enqueue server (SAP<SID>AEN)
    • ABAP message server (SAP<SID>AMS)

    The resources SAP<SID>AEN and SAP<SID>AMS have a HasParent/StartsMeAndStopsMe relationship to SAP<SID>A_STA.

SAP<SID>AER_X of Figure 1 contains these resources:

  • SAP<SID>AR_SRV [subsystem name SAP<SID>AR_SR], which models the ABAP ERS sapstartsrv process that must be active in order to start the ABAP ERS instance
  • SAP<SID>AERV, which models the VIPA associated with the ABAP ERS instance
  • SAP<SID>AR_STA [subsystem name SAP<SID>ARST], which models the ABAP ERS sapstart process that is the parent process of the ABAP enqueue replication server resource SAP<SID>AER.

SAP<SID>AER has an Externally/StartsMe relationship and a MakeAvailable/WhenAvailable relationship to SAP<SID>AR_STA.

Further details of Figure 1:
  • When the SAP system is configured with TCPIP based replication with a separate enqueue replication server instance the threshold definition for the SAP<SID>AEN application is as follows:
    Threshold Value
    Critical Number 1
    Critical Interval 01:00:00
    Frequent Number 1
    Frequent Interval 02:00:00
    Infrequent Number 1
    Infrequent Interval 12:00:00

    The critical threshold number of the enqueue server is set to 1. This setting means that SA z/OS® does not try to restart the enqueue server on the same LPAR. Instead, a failover to a different LPAR is triggered whenever the enqueue server terminates. When the SAP system is configured with EnqCF based replication (see Chapter 14) then a restart in-place of the enqueue server after a failure is possible without losing enqueue locks. Therefore, the threshold definition for the SAP<SID>AEN application should be as follows:

    Threshold Value
    Critical Number 5
    Critical Interval 00:10:00
    Frequent Number 3
    Frequent Interval 01:00:00
    Infrequent Number 3
    Infrequent Interval 12:00:00
  • The VIPA resource SAP<SID>ACV (in addition to being member of the SAP<SID>ASCS) is also member of the SYSPLEX MOVE PASSIVE group SAP<SID>ACV_X. Its purpose is to define a relationship between the enqueue server its VIPA and the enqueue replication server. The relationship of the SAP<SID>AER_X group is MakeAvailable/WhenAvailable(Passive/Weak) to the SAP<SID>ACV_X group.

    This ensures that the INGGROUP command (described in Table 1) in the application automation definitions of the SAP<SID>ACV resource is processed by SA z/OS prior to the decision where to place the enqueue replication server. Since SAP<SID>ACV_X is a MOVE group, only one VIPA is started or is active in the SYSPLEX at one time.

    Additionally, the SAP<SID>A_STA resource has a MakeAvailable/WhenAvailable(Active/Weak) relationship to the VIPA. This relationship ensures that the VIPA is up before the ABAP SCS instance is started via the sapstart resource (SAP<SID>A_STA).

  • The SAP enqueue replication server resource SAP<SID>AER is a member of the SAP<SID>AERS group, which in turn is a member of the SYSPLEX MOVE group SAP<SID>AER_X. This structure ensures that only one enqueue replication server is started or is active in the SYSPLEX at one time. For an explanation of the dependency and relationships between the enqueue server and the enqueue replication server, see Dependencies between the ABAP enqueue server and the enqueue replication server.
  • Additionally, the SAP<SID>AER_X group has a HasParent relationship to SAP<SID>AR_SRV. This relationship ensures that the sapstartsrv service of the ABAP ERS instance is active and able to start/stop the ABAP ERS instance.