IMS Connect, MSC, and TCP/IP generic resources

IMS Connect provides routing and connection management support for MSC links that connect to a TCP/IP generic resource group.

TCP/IP generic resources enable MSC links to be switched between participating IMS systems in an IMSplex without requiring system definition changes to the MSC partner systems outside of the IMSplex.

The IMS systems that participate in a TCP/IP generic resource group all specify a shared generic IMS ID in their respective IMS DFSDCxxx PROCLIB members. In IMS Connect, this generic IMS ID is specified on the GENIMSID parameter of the MSC configuration statement for each IMS system.

When IMS Connect receives the first MSC logical link request on a physical link for the TCP/IP generic resource group, IMS Connect broadcasts the request to all participating IMS systems in the group. IMS Connect routes the link request to the first IMS system to respond to IMS Connect.

When an IMS system accepts the link request, affinity is established between the IMS system and all logical links that use the physical link to the IMS system. Affinity persists for all logical links on a given MSC physical link until all logical links on the physical link terminate normally or the physical link path is stopped in IMS Connect. After the last logical link terminates and the affinity is released, the next link request on the physical link can establish affinity with a different IMS system.

You can display affinity information for a logical link in both IMS and IMS Connect. In IMS Connect, you can display affinity information by specifying any one of the following IMS Connect commands:
  • The IMS type-2 format command QUERY IMSCON TYPE(MSC) NAME(lclPlkid)
  • The IMS type-2 format command QUERY IMSCON TYPE(LINK) NAME(lclPlkid)
  • The WTOR format command VIEWMSC lclPlkid
  • The z/OS® MODIFY command QUERY MSC NAME(lclPlkid)

You can control which IMS system in a TCP/IP generic resource group accepts the first logical link request on a physical link. The easiest way to do this is to start the link from the IMS system in the generic resource group.

If the link must be started from the remote IMS system, you can control which IMS system accepts a link from either the TCP/IP generic resource group or IMS Connect. In the TCP/IP generic resource group, you can stop logons to the generic IMS ID in every IMS system in the generic resource group, except in the one that requires affinity. Alternatively, in IMS Connect you can stop all MSC physical link paths except the path to the IMS system that requires affinity.

To stop a physical link path in IMS Connect, issue any one of the following IMS Connect commands:
  • The IMS type-2 format command UPDATE IMSCON TYPE(MSC) NAME(lclPlkid) STOP(COMM)
  • The WTOR format command STOPMSC lclPlkid
  • The z/OS MODIFY command UPDATE MSC NAME(lclPlkid) STOP(COMM)