Stagger end-of-day time sample utility program (DFH$STED)
Statistics intervals can occur simultaneously across many CICS® regions in the same MVS™ image, and this can degrade performance. To prevent this, you should vary the statistics interval occurrence time for each CICS region. You can use the sample utility program, DFH$STED, to vary automatically the end-of-day time of each CICS region it is installed in, and therefore vary the interval occurrence time of these CICS regions.
For information about the end-of-day time and the system initialization parameter to set it, see Setting the statistics recording status, end-of-day time and recording interval.
- Make the appropriate changes for your environment
- Assemble the program into a library that is before SDFHLOAD in the DFHRPL concatenation
- Include the CSD group definition for DFH$STAT into your startup group list
- Add the sample program name to the 2nd phase list of programs in your PLTPI table
You should run the DFH$STED program in the third phase of CICS initialization (that is, during the second phase of PLT processing).
You can use the following three parameters to control how the end-of-day time is amended. These parameters are part of the source of DFH$STED. To change them, you must modify the source of DFH$STED, which is located in SDFHSAMP.
- EODDRIFT
- Specifies the end-of-day drift time; that is, the maximum
allowable drift from the original end-of-day time.
This enables you to stagger the end-of-day time of each of your CICS regions by a pseudo-random amount (based upon the time of day at which the program is executing), up to a user-specified maximum value. Since intervals are calculated using the end-of-day as a base time, the occurrence of intervals are staggered by this pseudo-random drift time. The default is ten minutes.
- EODTIME
- Specifies whether the end-of-day time before amendment by the
drift value should take the current value (that is, 00:00:00 if started
COLD, or the value at previous CICS shutdown
if AUTO or WARM started).
You should set this field to CURRENT if you need the current end-of-day time, or FIXED if you need a new end-of-day time. If you specify FIXED, you should specify the new time on the EODFIXED parameter. The default value of the EODTIME parameter is FIXED.
- EODFIXED
- Specifies the new logical end-of-day time, in the form hhmmss, as a hexadecimal value in the range X'000000' through X'235959'. Specify the EODFIXED parameter only if you also specify the EODTIME=FIXED parameter. When used in conjunction with a finite value of EODDRIFT, the drift value specified by the EODDRIFT parameter is applied to the new end-of-day specified by the EODFIXED parameter. When a zero value is specified for the EODDRIFT parameter, the end-of-day time is as specified for the EODFIXED parameter. The default setting is X'000000' (midnight).