Using VSAM extended addressability capabilities

DFSMShsm supports VSAM KSDS extended addressability (EA) capabilities that use any of the following serialization techniques for accessing its control data sets: record level sharing (RLS) access mode, CDSQ serialization, or CDSR serialization. VSAM EA capabilities allow each cluster to exceed the 4 GB size. The MCDS and BCDS can span up to four unique KSDS clusters. The OCDS is limited to a single cluster. The same serialization technique must be used to access all control data sets.

Rules: Use the following rules when you use CDS extended addressability:

CDS EA in RLS mode: Specify CDSSHR=RLS for all DFSMShsm systems sharing the same control data sets.
CDS EA with CDSQ serialization: Specify the CDSQ=YES and CDSR=NO for all DFSMShsm systems sharing the same control data sets.
CDS EA with CDSR serialization: Specify the CDSQ=NO and CDSR=YES for all DFSMShsm systems sharing the same control data sets.
CDS EA with CDSQ and CDSR serialization: Specify the CDSQ=YES and CDSR=YES for all DFSMShsm systems sharing the same control data sets.
Multicluster control data sets: Multicluster control data sets can still use CDSQ, CDSR, or CDSQ and CDSR. They cannot be defined with key ranges, but must use dynamic allocation support.

Requirements: The following requirements may affect your use of extended addressability for your control data sets:

Mixing extended function (EF) clusters and non-EF clusters is permissible because each cluster is treated as a separate entity. However, if any cluster is accessed in RLS mode, then all clusters must be accessed in RLS mode.
Examine your disaster recovery plans to ensure that your disaster recovery site can support the use of EA control data sets with the proper serialization. You can use CDSQ serialization, CDSR serialization, or RLS.

Note:

You can define each CDS as EA or non-EA; however, you do not have to define all control data sets as EA or non-EA.
You can define each MCDS or BCDS cluster as EA or non-EA.
Extended addressability control data sets can be single cluster and multivolume or multicluster and multivolume.
The MCDS and the BCDS can be represented by up to 4 KSDS EA data sets. Separate clusters reduce backup processing time by allowing parallel operations. In addition, if only one cluster is damaged or lost, the recovery time to forward recover this one cluster would be reduced.