ALTER PSID on z/OS

Use the MQSC command ALTER PSID to change the expansion method for a page set.


Use MQSC commands

For information on how we use MQSC commands, see Performing local administration tasks using MQSC commands.

Parameters not specified in the ALTER PSID command result in the existing values for those parameters being left unchanged.

We can issue this command from sources CR. For an explanation of the source symbols, see Use commands on z/OS®.

Synonym: ALT PSID

ALTER PSID

ALTER PSID ( psid-number ) EXPAND(USER)EXPAND(SYSTEM)EXPAND(NONE)


Parameter descriptions for ALTER PSID

    (psid-number)
    Identifier of the page set. This is required.

    EXPAND
    Controls how the queue manager should expand a page set when it becomes nearly full, and further pages are required in it.

      USER
      The secondary extent size that was specified when the page set was defined is used. If no secondary extent size was specified, or if it was specified as zero, then no dynamic page set expansion can take place.

      At restart, if a previously used page set has been replaced with a data set that is smaller, it is expanded until it reaches the size of the previously used data set. Only one extent is required to reach this size.

      SYSTEM

      A secondary extent size that is approximately 10 per cent of the current size of the page set is used. It might be rounded up depending on the characteristics of the DASD.

      The secondary extent size that was specified when the page set was defined is ignored; dynamic expansion can occur if it was zero or not specified.

      NONE
      No further page set expansion is to take place.


Usage note

We can use ALTER PSID to reset an internal IBM MQ indicator that prevents the pageset from being expanded; for example, after the data set has been ALTERed to ADDVOLUMES.

In this instance, although the EXPAND keyword must be specified with a value, we do not have to change the value from that already configured. For example, if DISPLAY USAGE shows pageset 3 configured with EXPAND(SYSTEM), you issue the following command to allow IBM MQ to retry pageset expansion:
ALTER PSID(3) EXPAND(SYSTEM)