Specifies that the DFSMShsm being started will run in a particular multiple-image or single-image environment.

Because this keyword is not normally specified, it has no default value. Its main uses are for testing and for merging multiple CDSs.

When you specify NO for this keyword, DFSMShsm does no multiple-host serialization; no other system should be concurrently processing this set of CDSs. The HOSTMODE of this DFSMShsm can only be MAIN. For performance reasons, specify NO in a single image environment with no auxiliary hosts and where the index of the MCDS is on a DASD device that is configured as shared.

When you specify YES for this keyword, DFSMShsm does multiple-host serialization of the type requested by the CDSQ and CDSR keywords.

When you specify RLS for this keyword, DFSMShsm performs multiple-host serialization using record level sharing (RLS). When RLS is specified, the CDSs are accessed in RLS mode and any values specified for CDSQ and CDSR are ignored.

If you do not specify the CDSSHR keyword in the startup procedure, DFSMShsmperforms multiple-host serialization if the index component of the MCDS resides on a DASD volume that has been SYSGENed as SHARED or SHAREDUP.