Global resource serialization (GRS) is a z/OS element designed to protect the integrity of resources in a multiple DFSMShsm host environment. By combining the systems that access the shared resources into a global resource serialization complex and by connecting the systems in the GRS complex with dedicated communication links, GRS serializes access to shared resources. User data sets are protected by associating them with the SYSDSN resource and then passing the SYSDSN token to the other images in the GRSplex.

The SYSDSN resource, provided by using the ENQ and DEQ macros, is passed to cross-system (global) enqueues. DFSMShsm shares its resources according to z/OS-defined ranges of control known as scopes in GRS terminology.

In a multiple DFSMShsm host environment where GRS is used for CDS serialization, functional processing, and some data set level serialization, the integrity of DFSMShsm resources is dependent on the QNAME=ARCENQG generic resource name being propagated to all systems.

In a sysplex environment, a GRSplex is one or more z/OS systems that use global serialization to serialize access to shared resources. You can now place multiple HSMplexes (one or more installed processors that share common MCDS, BCDS, OCDS, and journals) in the same GRSplex, because DFSMShsm can now translate minor global resource names to avoid interference between HSMplexes. For more information on global serialization in a sysplex, see DFSMShsm in a sysplex environment.

In a GRS environment, some available DFSMShsm and JES3 options can affect the overall performance of DFSMShsm. For more information about exclusion and conversion RNLs, refer to z/OS MVS Planning: Global Resource Serialization.