One or more processors with DFSMShsm installed and running that share a common MCDS, OCDS, BCDS, and journal is called an HSMplex. One or more MVS™ systems that use global serialization to serialize access to shared resources (for example, data sets on shared DASD volumes) is called a GRSplex.

If two HSMplexes exist within a sysplex environment, one HSMplex interferes with the other HSMplex whenever DFSMShsm tries to update CDSs in non-RLS mode or when it is performing other functions, such as level 1 to level 2 migration. This interference occurs because each HSMplex, although having unique resources, uses the same resource names for global serialization.

Within a GRSplex, you can now place multiple HSMplexes into a single GRSplex. The single GRSplex serialization function allows DFSMShsm to translate minor global resource names to unique values within the HSMplex, thus avoiding interference between HSMplexes.