MSC coexistence considerations

You can connect an IMS 15 Transaction Manager subsystem to other supported versions of IMS by using Multiple Systems Coupling (MSC).

The following IMS versions can coexist with an IMS 15 system in an MSC network:

  • IMS 14 (5635-A05)
  • IMS Version 13 (5635-A04)

For an IMS that was generated with MSC resources to coexist with IMS 15, any MSC user exits that access MSC LLB control blocks (logical links) or MSC LCB control blocks (physical links) must be changed to access those blocks using callable services or DSCBTS services. This change is required regardless of whether dynamic MSC is enabled.

You might need to update an MSC resource definition in an IMSplex in which an IMS 15 system that uses an IMSRSC repository coexists with an IMS Version 13 or earlier IMS system. In this scenario, the MSC resource updates that are made on the IMS 15 system by using the UPDATE commands must be made on the IMS Version 13 or earlier IMS systems by coding stage-1 system definition macros.

If the IMSRSC repository support for dynamically defined MSC resources is enabled for IMS 15, apply the following coexistence APARs to the RM systems in the IMSplex:
  • IMS 14: APAR/PTF PI49208/UI32429
  • IMS Version 13: APAR/PTF PI49334/UI32565
Use one of the following methods to install the coexistence APARs that are listed in the preceding list:
  • First, install IMS Version 13 APAR/PTF PI49334/UI32565, and the IMS 14 preconditioning APAR/PTF PI49208/UI32429 on all RM systems in the IMSplex. Then, install the IMS 14 preconditioning APAR/PTF PI45186.
  • Install all of the following APARs on all RM systems in the IMSplex at the same time:
    • IMS Version 13 APAR/PTF PI49334/UI32565
    • IMS 14 preconditioning APAR/PTF PI49208/UI32429
    • IMS 14 preconditioning APAR/PTF PI45186