5.4: Changes to system initialization parameters

Several performance-related CICS® system initialization table (SIT) parameters are changed in CICS TS 5.4. This section outlines changes to the SIT parameters that have the most impact on CICS performance. All comparisons to previous limits or default values refer to CICS TS 5.3.

For a detailed view of changes to SIT parameters in CICS TS 5.4, see Changes to SIT parameters.

EDSA limit (EDSALIM) parameter

The minimum value for the EDSALIM parameter increased from 48 MB to 64 MB. The value that is specified for the EDSALIM parameter can be a maximum of 2047 MB, specified in multiples of 1 MB.

For more information, see EDSALIM system initialization parameter.

Default runaway task time (ICVR)

The minimum value for the ICVR value reduced from 500 ms to 250 ms. The default value is reduced from 5000 ms to 2000 ms. The value that is specified for the ICVR parameter can be a maximum of 2,700,000 ms in multiples of 250 ms.

For more information, see ICVR system initialization parameter.

Maximum open TCBs (MAXOPENTCBS)

The minimum value for the MAXOPENTCBS parameter increased from 1 to 32.

If the MAXOPENTCBS parameter is not specified, CICS sets the parameter automatically, based on the current value of the MXT system initialization parameter. The value of the MAXOPENTCBS parameter is calculated by using the same algorithm implemented in CICS TS 5.1, as shown in the following example:

MAXOPENTCBS = (2 x MXT) + 32

For more information about the MAXOPENTCBS parameter, see MAXOPENTCBS.

Maximum SSL TCBs (MAXSSLTCBS)

The default value for the MAXSSLTCBS parameter increased from 8 to 32.

For more information about the MAXSSLTCBS parameter, see MAXSSLTCBS system initialization parameter.

RACF synchronization (RACFSYNC)

The RACFSYNC system initialization parameter specifies whether CICS listens for type 71 Event Notification Facility (ENF) events.

RACF® sends a type 71 ENF signal to listeners when a CONNECT, REMOVE, or REVOKE command changes a user's resource authorization. If RACFSYNC=YES is specified in a CICS TS 5.4 environment, when CICS receives a type 71 ENF event for a user ID, all cached user tokens for the user ID are invalidated, irrespective of the setting of the USRDELAY parameter.

Subsequent requests from that user ID force a full RACF RACROUTE VERIFY request, which results in a refresh of the user's authorization level. User tokens for tasks that are currently running are not affected. In addition to the RACF RACROUTE VERIFY processing, a type 71 ENF signal will also make Db2® threads for the associated user ID issue a full sign on when they are next reused.

Note: In the configuration where type 71 signals are issued for large numbers of users simultaneously, combined with large numbers of connections to Db2, the temporary performance overhead can be significant while the full sign on processing across all affected Db2 threads is completed.

To reduce the impact of type 71 ENF processing, make updates to large numbers of RACF users during off-peak periods.

For more information about the RACFSYNC parameter, see RACFSYNC system initialization parameter.

Sign on for a preset user ID (SNPRESET)

The new SNPRESET parameter is provided to allow the sharing of access control environment element (ACEE) control blocks. This process can save 31-bit storage and CPU. The SNPRESET parameter takes one of the following values:

UNIQUE: When signing on a preset user ID terminal, the ACEE is built with entry port information. Every preset terminal has a unique ACEE that is associated with the user ID and terminal. This is the default.
SHARED: When signing on a preset user ID terminal, the ACEE is built without entry port information. All preset terminals with the same user ID use the same ACEE.

If you audit data that is based on the terminal of a preset user ID, use SNPRESET=UNIQUE.

If you do not need information that is based on the terminal of a preset user ID, you can save storage by selecting SNPRESET=SHARED.

Note: In the event of a security violation with SNPRESET=SHARED, the netname of the terminal will not show in the DFHXS1111 message.

For more information about the SNPRESET parameter, see SNPRESET.

z/OS Workload Manager Health API (WLMHEALTH)

CICS TS 5.4 introduces the new SIT parameter WLMHEALTH. For more details about the use of the z/OS® Workload Manager Health API in CICS, see z/OS WLM Health API: CICS TS V5.4.

For more information about the WLMHEALTH parameter, see WLMHEALTH.