Auxiliary or Main Temporary Storage

You can choose main or auxiliary temporary storage as a trade off between using more real storage (main) and increasing disk I/O activity (auxiliary). The CICS® interface makes heavy use of temporary storage, especially during SELECT PROCESS and SELECT STATISTICS operations.

CICS Dynamic Storage Area (DSA) Usage

The CICS interface uses the CICS DSA as follows:

  • Approximately 1 KB is used by the CICS Task Control global exit.
  • Approximately 10–20 KB is used for transaction-related storage and temporary storage records by the DGA and DGAA transactions.

In addition, the SELECT PROCESS (SP) and SELECT STATISTICS (SS) functions are heavy users of CICS Temporary Storage. Results returned by these functions are written to Temporary Storage as a series of 300-byte records.

Parameters are provided on the DTF NODE configuration screen of the DGAA transaction (OUTPUT RECORD LIMIT) and on the IUI.NODE statement of the IBM® Connect:Direct® CICS Configuration Load program (TDLIMIT) to limit the amount of data returned by these commands.

Above-the-Line Storage

Non-CICS storage above the 16-megabyte line is used by the CICS interface as follows:

  • Approximately 340 KB is used for IBM Connect:Direct API programs.
  • The CICS interface signon table, node table, and subtask tables are allocated above the line, with the total amount required calculated as follows.
    36 + (18*(T+W)) + (304*S) + (224*N) + (144*T)

The following table describes the variables in the preceding example:

Variable Description
T The sum of the maximum subtask per node values or all nodes eligible to be signed on to by the CICS interface (MAXIMUM WORKER SUBTASKS on the DTF NODE configuration screen or VTAM®.SESSIONS on the IUI.NODE parameter of the CICS interface Configuration Load program).
W The total number of entries in the WORK QUEUE for all DTF nodes.
S The value of the MAX.SIGNON parameter of the Configuration Parameters screen or CONTROL.PARMS statement of the Configuration Load program.
N The number of nodes eligible to be signed on to by the CICS interface (the number of DTF.NODE records defined in the CICS interface configuration file).