Daylight Savings Time

It’s getting close to that time of year again, when the clocks will “spring forward” an hour, and we have to remember what (if anything) needs to be done in CICS when the system clock is adjusted. There are options besides bouncing your CICS regions.

If your system time will be set before midnight and you have AUTORESETTIME set to YES in your CICS SIT table, CICS will automatically set its clock to the system clock at midnight. Note that the default for AUTORESETTIME is NO.

To synchronize the CICS clock to the system clock any other time, you can do so with a CEMT PERFORM RESET command, or EXEC CICS RESETTIME within a program.

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CICS and Daylight Savings Time

Time changes tonight, so it’s time to make sure that our CICS systems are in sync with the operating system clock when that occurs. The best way to accomplish this depends on the method that the operating system clock is set.

If your operating system clock is set as an offset from GMT, then all you will need to do for the operating system clock is to change the offset at the appropriate time. If you do so before midnight and you have AUTORESETTIME in your CICS SIT tables set to yes, you are done; at midnight, CICS’s will adjust their clocks. If you change the offset after midnight or do not have AUTORESETTIME set to yes (default is no), you will need to perform a CEMT PERFORM RESET for the CICS clocks to adjust.

If your operating system clock is set to the hardware clock and not to a GMT offset, then you are probably planning to perform a POR (power-on reset). If so, your CICS systems will have the correct time when they are brought up. You are probably having to let the system sit idle for an hour in the fall if you are performing a POR so that your applications do not encounter times that have already occured. If this is your standard mode of operation, you can make your life easier if you investigate having your operating system clock set as an offset from GMT time.