ABCs of z/OS System Programming Volume 3 - IBM Redbooks

► Place the SHCDSs on volumes with global connectivity because VSAM RLS processing is
only available on those systems that currently have access to the active SHCDS.
► The SHCDSs must not be shared outside the sysplex.
► Use SHAREOPTIONS(3,3).
► If SMS-managed, use a storage class with guaranteed space for the SHCDSs.
► Use the naming convention: SYS1.DFPSHCDS.qualifier.Vvolser, where:
– qualifier is a 1- to 8-character qualifier of your choice.
– volser is the volume serial number of the volume on which the data set resides.
► All SHCDSs are to be of the same size.
► An SHCDS can have extents only on the same volume.
Both the primary and secondary SHCDS contain the same data. With the duplexing of the
data, VSAM RLS ensures that processing can continue in case VSAM RLS loses connection
to one SHCDS or the control data set got damaged. In that case, you can switch the spare
SHCDS to active.
Note: The SMSVSAM address space needs RACF UPDATE authority to
SYS1.DFPSHCDS.
JCL to allocate the SHCDSs
You can use the sample JCL in Figure 7-19 to allocate your SHCDSs.
//STEP01 EXEC PGM=IDCAMS
//SYSPRINT DD SYSOUT=*
//SYSIN DD *
DEFINE CLUSTER( -
NAME(SYS1.DFPSHCDS.PRIMARY.VTOTSMA) -
VOLUMES(TOTSMA) -
MEGABYTES(10 10) -
LINEAR -
SHAREOPTIONS(3,3) -
STORAGECLASS(GSPACE))
DEFINE CLUSTER( -
NAME(SYS1.DFPSHCDS.SECONDRY.VTOTCAT) -
VOLUMES(TOTCAT) -
MEGABYTES(10 10) -
LINEAR -
SHAREOPTIONS(3,3) -
STORAGECLASS(GSPACE))
DEFINE CLUSTER( -
NAME(SYS1.DFPSHCDS.SPARE.VTOTSMS) -
VOLUMES(TOTSMS) -
MEGABYTES(10 10) -
SHAREOPTIONS(3,3) -
LINEAR -
STORAGECLASS(GSPACE))
Figure 7-19 Allocating VSAM RLS SHCDSs
To calculate the size of the sharing control data sets, follow the guidelines provided in z/OS
DFSMSdfp Storage Administration Reference, SC26-7402.
Chapter 7. DFSMS Transactional VSAM Services 403