Resource recovery

Resource recovery consists of the protocols and program interfaces that allow an application program to make consistent changes to multiple protected resources. The external CICS® interface supports resource recovery.

A CICS server program that is invoked by an external CICS interface request can update recoverable resources; the changes are committed when the mirror transaction in the CICS server region takes a sync point. The client program can determine when sync pointing should occur. There are two options:
  • Resource recovery controlled by the CICS server regions. In this case, changes to recoverable resources are committed at the completion of each DPL request, independently of the client program. Also, in addition to the sync point taken when the server program returns control to CICS (the SYNCONRETURN option), the server program can take explicit sync points during execution.
  • Resource recovery controlled by the EXCI client program with the support of recoverable resource management services (RRMS). When the client program requests it, updates made by the server program in successive DPL requests are committed together.

    To support this option, CICS and the external CICS interface both use resource recovery services (RRS), the z/OS® sync point manager 1 , which is an MVS™ component of recoverable resource management services (RRMS). In the context of RRMS, CICS is a resource manager ; the client program can issue requests to other resource managers, and have resources owned by those resource managers committed in the same unit-of-recovery (UR). 2

These options are controlled as follows:
  • By the DPL_opts parameter of the DPL_request.
  • By the SYNCONRETURN option, either specified or omitted, on the EXEC CICS LINK PROGRAM command.
If you specify SYNCONRETURN, a sync point is taken on completion of each DPL request. If SYNCONRETURN is omitted, a sync point is taken when the client program requests it using the interfaces described in Use of sync points in the client program.
1 RRMS comprises three z/OS components: registration services, context services, and resource recovery services (RRS)
2 A unit of recovery is analogous to a CICS unit of work