Multiple CSI data sets can be:

• Separate from each other, each with its own global zone.
• Connected by ZONEINDEX entries to a single global zone. (The global zone must be in one of the CSI data sets.)

Multiple CSIs enable you to use more than one VSAM data set for the global, target, and distribution zones. These are some reasons for having multiple CSI data sets:

• Your system may need multiple CSIs because of the characteristics of a particular installation—its programming support, its backup and update needs, and its need for added security and data integrity. For example, keeping libraries and their associated zones synchronized when you dump them for backup is easier if you keep them on the same physical DASD.
• Your system may need multiple CSIs if the support teams for different subsystems—such as MVS™, CICS®, IMS™, and NCP—are at different places.
• You may want to be able to run more than one background SMP/E job at a time. When SMP/E needs to process a zone, it cannot request access to that specific zone; it must request access to the CSI data set containing that zone. If your zones are in separate CSI data sets, processing for one zone does not prevent access to another zone.