The Compress for IMS modules are provided to support the currently available IMS versions: so release r19 supports IMS v12, v13 and v14. Stub modules will call the relevant IMS version specific modules. For example, the IMSHRINK stub calls 1 of 3 modules dependent on the version of IMS:
The 1 letter suffix identifies the IMS version supported by that release. The suffixing we use for these version specific modules is as follows:
IMS version Module suffix
Note there is no requirement to reassemble any modules when upgrading IMS. However, if the CA Compress for IMS modules have been copied from the distributed CIMTLOAD to another library, such as the IMS RESLIB, then you need to ensure that all the required modules are copied.