Catalog alias
An entry in the master catalog that sends every dataset name with a given high-level qualifier to a particular user catalog.
Also written alias entry, DEFINE ALIAS, HLQ alias, user catalog alias
z/OS has one master catalog for each system and usually many user catalogs. Most datasets are recorded in user catalogs, not in the master. A catalog alias is what connects the two.
An alias is an entry in the master catalog for a high-level qualifier. ZBANK as an alias that points to the user catalog CATALOG.ZBANK means that every dataset whose name starts with ZBANK is looked up in, and recorded in, that user catalog. Aliases are created with the IDCAMS command DEFINE ALIAS and can be listed with LISTCAT.
Sites protect the master catalog carefully, because the system cannot run without it. So when a new high-level qualifier is introduced, for a new application or a new user, a system programmer or storage administrator defines its alias first.
Without an alias, new datasets with that qualifier are catalogued in the master catalog, which sites want to avoid. If datasets for a new project seem to be catalogued in the wrong place, or LISTCAT shows them in the master catalog, a missing alias is the likely cause.
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- CatalogThe system's index of where datasets live, so you can refer to a dataset by name without knowing which disk it is on.
- High-level qualifierThe first part of a dataset name, which usually identifies the owner and drives how security and storage rules apply.
- IDCAMSThe utility used to create, list, copy and delete datasets, and the standard tool for anything involving VSAM.
- LISTCATA TSO command that lists what the catalog knows: dataset names and which catalog holds them.
- System programmerThe person who installs, configures, tunes and upgrades the operating system and its subsystems.