Problem:
We have had a request to not shut down the systems for IPL during the DST window. We have always shutdown each system and "waited" for 1 hour during the Autumn clock change. Now we want to change that.
We have 2 physical machines and 5 production LPARs in a Parallel Syslex. we have z/OS 1.8 and z/OS 1.6, CICS/TS 2.3, IMS 8.1 and IMS 7.1 and DB2 V8.
Currently we have an ETR that reflects UTC, and the SYSPLEX timer which reflects local time, there is no offset set.
We wish to be able to just close down most of our applications but leave a DB2 and IMS system up for one of our client companies without the need to IPL. No investigation has been done yet for the applications ability to handle this, we are just at the moment looking at the z/OS side of things.
Answer:
Our site doesn't do anything on clock change. We have the sysplex timer set up with an external time clock that copes with any time changes. There is a setting you can put on the timer to help with the clock change. See the Redbook z/OS Planned Outage Avoidance (SG24 7328).
DB2 and CICS both run on UTC internally so the clock change doesn't affect them. The only oddity you see is with USS during the summer. You have to remember that the time shown on last updated date/time is UTC not local time.