DEFINE PSID on z/OS

Use the MQSC command DEFINE PSID to define a page set and associated buffer pool.


Use MQSC commands

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

We can issue this command from sources 1CR. For an explanation of the source symbols, see Sources from which we can issue MQSC commands on z/OS .

Synonym: DEF PSID


DEFINE PSID

DEFINE PSID ( psid-number ) BUFFPOOL(0)BUFFPOOL(integer)DSN(data set name)EXPAND(USER)EXPAND(SYSTEM)EXPAND(NONE)


Usage notes for DEFINE PSID

The command can be used in two ways:

  1. At restart, from the CSQINP1 initialization input data set, to specify your standard page sets:

    • We cannot specify the DSN keyword if issuing the command from CSQINP1.
    • If more than one DEFINE PSID command is issued for the same page set, only the last one is processed.

  2. While the queue manager is running, to dynamically add a page set:

    • The command must specify the DSN keyword and can be issued from either of the following:

      • The z/OS console.
      • The command server and command queue by means of CSQUTIL, CSQINPX, or applications.

    • The page set identifier (that is the PSID number) may have previously been used by a queue manager. It should therefore be freshly formatted by a FORMAT(RECOVER) statement in CSQUTIL, or formatted by with a FORMAT(REPLACE) in CSQUTIL.
    • We cannot dynamically add page set zero.
    • The BUFFPOOL parameter can specify a currently unused buffer pool. If the buffer pool was defined in CSQINP1 but not used by any PSID, then the number of buffers specified there is created if the required virtual storage is available. If this is not available, or if the buffer pool was not defined in CSQINP1, the queue manager attempts to allocate 1000 buffers. If this is not possible, 100 buffers are allocated.
    • We should update your queue manager started task procedure JCL and your CSQINP1 initialization input data set to include the new page set.

One of the messages CSQP042I or CSQP041E is output when the command is complete.

We must use the ALTER PSID command to dynamically change the expansion method. For example, to change the EXPAND parameter from USER to SYSTEM, issue the following command:
ALTER PSID(page set id) EXPAND(SYSTEM)

We can use the DISPLAY USAGE TYPE(PAGESET) command to display information about page sets (see DISPLAY USAGE on z/OS ).


Parameter descriptions for DEFINE PSID

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

    A one-to-one relationship exists between page sets and the VSAM data sets used to store the pages. The identifier consists of a number in the range 00 through 99. It is used to generate a ddname, which references the VSAM LDS data set, in the range CSQP0000 through CSQP0099.

    The identifier must not be the same as any other page set identifier currently defined on this queue manager.

    BUFFPOOL( integer )
    The buffer pool number is in the range zero through 99. This is optional. The default is zero.

    If the buffer pool has not already been created by a DEFINE BUFFPOOL command, the buffer pool is created with 1000 buffers, and a LOCATION value of BELOW.

    If the psid-number is zero, the buffer pool number must be in the range 0 to 15, otherwise the command fails, and the queue manager does not start.

    DSN( data set name )
    The name of a cataloged VSAM LDS data set. This is optional. There is no default.

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

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

      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 can be rounded up depending on the characteristics of the DASD.

      NONE
      No further page set expansion is to take place.

Parent topic: MQSC commands