Migration planning for Named Counter and Shared Temporary Storage servers

Start of changeNamed Counter servers and Shared Temporary Storage servers can be at different levels in different MVS™ images, even when connected to the same coupling facility structure. They still function correctly in these circumstances. Each MVS image only uses a single server for each coupling facility structure, so all accesses to the coupling facility structure from each MVS image execute server code that is at the same level.End of change

Upgraded Named Counter servers and Shared Temporary Storage servers include new support for automatic restart (using ARM) and system-managed processes (rebuild and duplexing). The existing data in the coupling facility is not affected by switching to the new level of server code, and can even be shared between old and new servers running on different MVS images. Existing CICS® TS 1.3 regions can work with the new level of server, with the very minor exception that the CICS TS 1.3 EXEC-level named counter interface will report an exception if the CICS TS for z/OS, Version 3.1 named counter server indicates that system-managed rebuild is in progress, whereas the CICS TS for z/OS, Version 3.1 EXEC interface simply waits and retries in that situation.

A CICS TS for z/OS, Version 3.1 region can use a CICS TS 1.3 server, although the normal rule is that servers should be at the higher level.

All of the CF-related servers including the named counter server can be closed down immediately using the server CANCEL command.

There is no difference between the temporary storage server and the named counter server relating to recovery, in that both servers store all of their data in the coupling facility structure, so it will be lost if the structure fails or the coupling facility is re-IPLed. There may be a distinction from the application point of view, in that the scratch pad information stored in the temporary storage structure may be less important to continuous operation than sequence numbers stored in named counters.

The Application Programming Guide contains a section on Named Counter Recovery considerations. In a production environment, it is important to have some separate means of recreating the named counters if the coupling facility structure is lost, for example by determining the latest used counters from data bases.

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