In North America and Europe we change our clocks twice a year for daylight savings time. The actual date of the change is different in North America and Europe. The procedures outlined below are provided as guidelines for ASG-TMON products, to be followed when setting system clocks. The issues with doing this are in software products like ASG-TMON that are logging time stamped data. During the spring time change when we set our clocks forward this is not an issue. In the spring, to change the clock, all that needs to be done for ASG monitors is to shut them down, IPL with the time change, and start the Monitors.

Setting the hardware clock back one hour in the fall is a different matter. This would mean duplicate time stamps on logged data. Duplicate time stamps would result in incorrect information in reports and summarized data would be incorrect. The following procedure will protect the integrity of the TMON Data Logging Services files. This procedure is applicable to TMON versions 2.6 and 2.7.

Procedure A

This procedure does not require that the COLLECTION file be initialized or reallocated; however, there could be duplicate time-stamps on archived transactions run during the overlapping time change. A system shutdown is required.

1. Stop all CICS/TS and CICS/VSE partitions.
2. If TMON for CICS/TS (VSE) is being used enter the following DLS commands for each of the TMON log-groups that are being used:
   MSG pp,D=SWAP=TMONx (pp = the DLS partition and x = the TMON log-group (A, B, etc.)
   When the archive and purge jobs have completed for each of the log-groups continue to step 3.
   
3. If TMON for CICS/VSE is being used submit the job that is used to dump the collection file (program TMV608) for each of the CICS/VSE partitions.
   When the archive and purge jobs have completed for each of the log-groups continue to step 4.
4. If TMON for VSE is being used submit the DCSSTOP job to terminate the Data Collection Service. Enter the following DLS command for the TVSEA log-groups.
   MSG pp,D=SWAP=TVSEA (pp = the DLS partition)
   When the archive and purge jobs have completed for each of the log-groups continue to step 5.
5. Terminate the Data Logging Service partition.
6. After IPL and setting the TOD clock, restart the system normally.

Procedure B

This procedure does not require that the COLLECTION file be initialized or reallocated. It requires a system shutdown and waiting for the amount of the change of time in your time zone.

1. Shut down CICS and all other applications.
2. IPL with the new time.
3. Wait one hour from the time of IPL.
4. Start up CICS and other applications as required.