CATALOG ALIAS field (CATALOG subsystem parameter)

The value of the CATALOG ALIAS field specifies the high-level qualifier for VSAM data sets that are to be used by the Db2 catalog and directory.

The installation CLIST also uses the value in the CATALOG ALIAS field to customize the following statements in Db2 installation and migration jobs:

The NAME parameter of the DEFINE ALIAS statement for the optional VSAM ICF user catalog for Db2 data sets (job DSNTIJCA)
The CATALOG parameter of AMS DELETE and DEFINE statements for Db2 catalog (DSNDB06), Db2 directory (DSNDB01), active logs, and bootstrap data sets (jobs DSNTIJDE and DSNTIJIN)
The VCAT parameter of various CREATE STOGROUP statements (jobs DSNTIJTM, DSNTIJSG, DSNTEJ1, DSNTEJ2A, and DSNTEJ3M)

Acceptable values:	1–8 characters
Default:	DSNCAT
Update:	See Changing the high-level qualifier for Db2 data sets
DSNZP`xxx`:	DSN6SPRM CATALOG

VSAM data set cataloging options

The installation jobs classify the Db2 VSAM data sets, which include recovery log, subsystem, and user data sets. You must create the catalog that defines these data sets through the VSAM ICF.

Recommendation: Use an ICF user catalog to classify all Db2 objects because you can use aliases for user catalogs. Multi-level ICF catalog aliases are acceptable. However, when you use the CREATE STOGROUP statement, you might need to use an alias for the VCAT option, which must be a single-level one- to eight-character name. You can use a master catalog, but only if the name of the master catalog is a single-level name that is one to eight characters.

Ensure that your alias conforms to your local naming conventions. If you are migrating, you should use the same ICF catalog aliases for Db2 12 that you used for your previous version because Db2 12 uses many of the data sets from your previous version that are already classified.

Whether you are installing or migrating, Db2 does not require you to catalog all Db2 VSAM data sets in the same ICF catalog nor use the same prefix or catalog alias. However, data sets for the Db2 catalog (DSNDB06) and Db2 directory (DSNDB01) must have the high-level qualifier that you specify in the CATALOG ALIAS field. See the following table for guidelines for the high-level qualifier of data sets. The BSDS is VSAM KSDS. The archive logs are sequential. All other data sets are VSAM linear data sets.

Table 1. Db2 data sets ICF catalog guidelines
Db2 data sets	Guidelines
Db2 directory (DSNDB01) Db2 catalog (DSNDB06)	The first-level qualifier of these data sets must be the value that you specify in the CATALOG ALIAS field. These data sets must be SMS-managed with allocation for extended format and extended addressability.
Active logs Bootstrap data set Default database (DSNDB04) Work file database	The first-level qualifier of these data sets does not need to match the value that you specify in the CATALOG ALIAS field. You can also catalog the data sets in different ICF catalogs using different prefixes.
Archive logs	The first-level qualifier of these data sets does not need to match the value that you specify in the CATALOG ALIAS field. If the archive log data set is allocated on disk, the data set must be cataloged according to the values of the ARCPFX1 or ARCPFX2 subsystem parameters, which are set through the COPY 1 PREFIX and COPY 2 PREFIX fields on panel DSNTIPH. If the archive log data set is allocated on a tape device, cataloging the data set is optional.
User table spaces User index spaces	The first-level qualifier of these data sets does not need to match the value that you specify in the CATALOG ALIAS field. You can catalog different user spaces in different ICF catalogs, using different prefixes.

You must provide any catalog connections for log and bootstrap data sets that you catalog apart from the Db2 directory and catalog data sets.

Recommendation: Add an alias for the proper catalog.

Although you can catalog two Db2 subsystems in the same ICF catalog, they must not share the same ICF catalog alias because the alias is the only parameter that makes the data set names unique.

Data set naming conventions

The value that you specify as the ICF catalog alias is also used as the high-level qualifier for Db2 directory and catalog VSAM data sets. The data sets for the Db2 directory and catalog databases and the default database are all VSAM linear data sets (LDSs). Their data set names have the following format:

dddddddd.DSNDBn.bbbbbbbb.xxxxxxxx.y0001.Accc

With the following definitions:

dddddddd

The high-level qualifier, which is the value that you supply for the CATALOG ALIAS field.

DSNDBn

A constant identifying this as a Db2 data set. For n, use C for a cluster name or D for a data component name.

bbbbbbbb

The database name. The system database names are:

DSNDB01: The Db2 directory database
DSNDB04: The default database
DSNDB06: The Db2 catalog database
DSNDB07: The default work file database

xxxxxxxx

The individual table space or index space.

y0001.Accc

The data set. For table spaces and index spaces that can be reorganized with SHRLEVEL CHANGE or SHRLEVEL REFERENCE, y can be I or J, depending on whether REORG has been run. For other table spaces and index spaces, y is I. ccc is the partition number of a partitioned table space or index space, or the relative data set number of a simple or segmented table space or index space.

For example, if the catalog alias is DSNCAT, one of the Db2 directory data sets is named:

DSNCAT.DSNDBD.DSNDB01.DBD01.I0001.A001

Similarly, one of the Db2 catalog data sets is named:

DSNCAT.DSNDBD.DSNDB06.SYSTSVEW.I0001.A001