Common Queue Server coexistence considerations

Restrictions limit how Common Queue Servers (CQSs) from earlier versions of IMS can coexist.

IMS 15 introduces the CQS automatic structure checkpoint function. An IMS 15 or later CQS that uses automatic structure checkpoint can coexist with IMS Version 13 and IMS 14 CQSs that are connected to the same shared queue structure. However, you can specify STRCHKPT= in the CQSSLxxx member of the IMS PROCLIB data set only in IMS 15 CQSs. Only IMS 15 or later CQSs can trigger automatic structure checkpoints, but all versions of CQS participate in the checkpoints.

General CQS coexistence rules

An IMS 15 CQS is downward compatible with IMS Version 13 and IMS 14. However, a CQS of an earlier IMS version is not upward compatible with a CQS of a later IMS version. The following general coexistence rules apply to CQS in IMS 15 at all IMS 15 release levels:
  • An IMS Version 13 or an IMS 14 can register with an IMS 15 CQS.
  • An IMS 15 cannot register with a pre-IMS 15 CQS.
  • An IMS 14 cannot register with a pre-IMS 14 CQS.
  • An IMS Version 13 cannot register with a pre-IMS Version 13 CQS.
  • User or vendor-written CQS clients that want to register with an IMS 15 CQS must be compiled with IMS Version 13 or later CQS macros.
  • User or vendor-written CQS clients that are compiled with the IMS 15 CQS macros cannot register with a pre-IMS 15 CQS.
  • User or vendor-written CQS clients that are compiled with the IMS 14 CQS macros cannot register with a pre-IMS 14 CQS.
  • User or vendor-written CQS clients that are compiled with the IMS Version 13 CQS macros cannot register with a pre-IMS Version 13 CQS.
  • An IMS Version 13 CQS, an IMS 14 CQS, and an IMS 15 CQS can connect to the same coupling facility structure.
  • Any supported version of CQS can run on the same central processing complex (CPC).
For example:
  • An IMS 15 CQS supports clients that are assembled with the IMS Version 13, IMS 14, or IMS 15 CQS macros.
  • A client that is assembled with the IMS 15 CQS macros can register only with an IMS 15 CQS. The IMS 15 client cannot register with an IMS Version 13 or an IMS 14 CQS. Similarly, a client that is assembled with the IMS 14 CQS macros cannot register with an IMS Version 13 CQS.