A page space is a system data set that contains pages of virtual storage. The pages are stored into and retrieved from the page space by the auxiliary storage manager. A page space is an entry-sequenced cluster that is preformatted (unlike other data sets) and is contained on a single volume. You cannot open a page space as a user data set.

A page space has a maximum size equal to 16␠777␠215 slots (records).

The considerations for defining a page space are much like those for defining a cluster. The DEFINE PAGESPACE command has many of the same parameters as the DEFINE CLUSTER command, so the information you must supply for a page space is similar to what you would specify for a cluster. A page space data set cannot be in extended format.

You can define a page space in a user catalog, then move the catalog to a new system, and establish it as the system's master catalog. For page spaces to be system managed, they must be cataloged, and you must let the system determine which catalog to use. Page spaces also cannot be duplicate data sets. The system cannot use a page space if its entry is in a user catalog.

When you issue a DEFINE PAGESPACE command, the system creates an entry in the catalog for the page space, then preformats the page space. If an error occurs during the preformatting process (for example, an I/O error or an allocation error), the page space's entry remains in the catalog even though no space for it exists. Issue a DELETE command to remove the page space's catalog entry before you redefine the page space.

Each page space is represented by two entries in the catalog: a cluster entry and a data entry. (A page space is an entry-sequenced cluster.) Both of these entries should be RACF-protected if the page space is RACF-protected.

The system recognizes a page space if it is defined as a system data set at system initialization time or if it is named in SYS1.PARMLIB. To be used as a page space, it must be defined in a master catalog.