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The data set names of the user catalogs are contained in the OS/390 master
catalog. Information necessary to locate the user catalogs is also defined in the
master catalog. The high-level-qualifiers of data sets that are to be cataloged in
each user catalog are also identified in the OS/390 master catalog.
OS/390 data set names are divided into qualifiers. The data set name consists of
up to 44 characters, grouped into qualifiers of up to eight characters each,
separated by periods. For example ″DEPT1.PAYROLL.YTD.DATA″ contains four
qualifiers. The high-level qualifier consists of the characters before the first
period in the data set name. It is also known as the catalog ″ALIAS″ name,
because it determines which user catalog OS/390 will search to find the data set
information. Thus the master catalog normally has many ALIAS name ″pointers″
to multiple user catalogs. An OS/390 user catalog may have many ALIAS names
associated with it. Each TSO user name will be associated with a particular user
catalog through an alias which must be defined for it.
The following diagram illustrates the master catalog to user catalog structure
relationship.
┌───────────┐ DEPT4 &
DEPT1 & JONES │ OS/390 │ PAYROLL
┌─────────────────┤ Master ├───────────────┐
│ │ Catalog │ │
│ └─┬───────┬─┘ │
│ DEPT2 │ │ DEPT3 │
││││
┌─────────┐ ┌─────────┐ ┌─────────┐ ┌─────────┐
│ User │ │ User │ │ User │ │ User │
│ Catalog │ │ Catalog │ │ Catalog │ │ Catalog │
└─────────┘ └─────────┘ └─────────┘ └─────────┘
DEPT1.DATA DEPT2.DATA DEPT3.JUNK DEPT4.DATA
DEPT1.CUST DEPT2.STATS PAYROLL.CURR
DEPT1.STORES PAYROLL.YTD
JONES.TSET.DATA
Figure 9. OS/390 Master and User Catalog Structure
The system searches for data sets by finding, via the master catalog, in which
user catalog the data set is cataloged. For example, for a data set named
DEPT1.PAYROLL.YTD.DATA, the master catalog would direct OS/390 catalog
management to the appropriate user catalog (identified by the DEPT1 ALIAS
name), and the data set information would then be retrieved from this user
catalog. The manual,
Managing Catalogs
, SC26-4914 contains more details about
the use of catalogs. It discusses aliases, catalog search order and so on, in
Chapter 2.
116 VSE to OS/390 Migration Workbook