Contents of the Master Catalog

The master catalog for a system contains entries for all the user catalogs that are used on the system and the aliases pointing to them. Other data sets that you should catalog in the master catalog are shown in Table 1.

Table 1. Master Catalog Entries
Entry types	Description/Example
User catalogs	Entries for all user catalogs used on the system.
Aliases	Entries for all aliases pointing to the user catalogs on the system.
Pagespaces	Entries for the pagespaces used on the system.
System software target libraries	The data sets used to run the system such as LINKLIB and ISPPENU.
Key operational data sets	Key operational data sets such as: PARMLIB data sets Parameter libraries for JES and TCP/IP SMS configuration data sets SMF data sets RACF® databases Couple data sets
Subsystem data sets	Subsystem data sets, such as those for IMS™, DB2®, or CICS®, especially when they are replaced.
Requirement: Data sets required during the IPL process must be cataloged in the master catalog. Recommendation: A master catalog should not contain entries for application or end user data sets. These should be contained in user catalogs that are pointed to by the appropriate aliases in the master catalog.

Figure 1 shows the relationship between master and user catalogs.

Figure 1. Relationship Between Master and User Catalogs. Parentheses indicate an entry in a catalog. Alias entries point to other entries in the same catalog. Arrows indicate the relationship between entries and the data sets they represent. The order of the entries in this example does not represent the order of entries in an actual catalog.

If your installation has multiple, interconnected systems, the master catalogs of each system can be connected to the master catalogs of each of the other systems. In other words, a master catalog on one system is a user catalog on the other systems.

You might want to combine SMS complexes into a single SMS complex and eliminate additional control data sets. To share the master catalog across an SMS complex see Sharing a Master Catalog and IPL Volume. If you are not running SMS, you can connect as many systems as is supported by the channel. RACF and appropriate alias naming conventions can prevent users on one system from cataloging data sets in the master catalog of another system. See Figure 1 for an example of interconnected master catalogs.

For ease of backup and recovery of the master catalog, no user data sets should be cataloged in the master catalog. If you deny update access to the master catalog for most of your users, there is typically much less update activity for the master catalog.

Each system must identify its master catalog. You identify the master catalog in the LOADxx member of SYS1.PARMLIB, or the SYSCATxx member of SYS1.NUCLEUS. (See Identifying the Master Catalog and Initial Configuration (SYSCATxx), and Bypassing SYSCATxx with LOADxx for more information.)