ASG-TMON™
Notes on Time Change



How to Change the System Clock in TMON for MQSeries

You can use one of two methods to change the system clock. Each method raises different considerations for TMON for MQSeries data; therefore, ASG recommends that you use the method and employ the TMON for MQSeries procedures that best meet the needs of your system. Methods also vary depending on whether the clock is being set ahead or back.

To set the system clock
You can re-IPL the system to reset the system clock.
Or
You can use the z/OS SET CLOCK command to change the GMT adjustment factor.

Re-IPLing the System

Setting the System Clock Ahead

Re-IPLing the system to set the system clock ahead does not affect TMON for MQSeries data because when you re-cycle z/OS, no activity is caught in flight.

Setting the System Clock Back

Re-IPLing the system to set the system clock back may cause TMON for MQSeries to record two sets of data for the same range of store clock (STCK) times.

To set the system clock back using the safest procedure

  1. Bring down all TMON Log File Services (LFS) and TMON for MQSeries regions.
  2. Re-IPL the system, resetting the system clock back.
    Note: Do not restart TMON for MQSeries or LFS until the revised time is later than the last used time before the reset.
  3. Restart the address spaces with no time overlap.

The disadvantage of this procedure is that it interrupts the use of your system for at least an hour. If you cannot endure an interruption of this length at your site, you can shorten it by replacing Step 3 with this alternate 2-step procedure:

  1. Dump the files that contain data you want to process.
  2. Reinitialize your files to ensure integrity of the data in the collection files.
    Note: Keep in mind that the data integrity you achieve by reinitializing the files applies only to the usability of the collection files. Your installation procedures must still take into consideration that reporting completed before the reset must be segregated from reporting completed after the reset to prevent duplicate reporting of the time interval during which the clock reset was done. You also must either restart history accumulation or address the idiosyncrasies of the reset interval.

Changing the GMT Adjustment Factor

This section presents common scenarios for setting the system clock ahead and back using the GMT adjustment factor.

Setting the System Clock Ahead (Standard Time)

These four scenarios are based on setting the system clock ahead.

You cannot re-cycle WebSphere MQ or TMON for MQSeries
  1. Use the DIS (disconnect) line command to disconnect TMON for MQSeries from all monitored queue managers.
  2. Set the system clock ahead.
  3. Use the CON (connect) line command to reconnect TMON for MQSeries to all monitored queue managers.
You cannot re-cycle WebSphere MQ; you can re-cycle TMON for MQSeries
  1. Stop TMON for MQSeries and LFS.
  2. Set the system clock ahead.
  3. Start TMON for MQSeries and LFS.
You can re-cycle WebSphere MQ; you cannot re-cycle TMON for MQSeries
  1. Shut down WebSphere MQ.
  2. Set the system clock ahead.
  3. Start WebSphere MQ.
You can re-cycle both WebSphere MQ and TMON for MQSeries
  1. Shut down WebSphere MQ.
  2. Shut down TMON for MQSeries.
  3. Set the system clock ahead.
  4. Start TMON for MQSeries.
  5. Start WebSphere MQ.

Setting the System Clock Back (Daylight Saving Time)

These four scenarios are based on setting the system clock back.

You cannot re-cycle WebSphere MQ or TMON for MQSeries
  1. Use the DIS (disconnect) line command to disconnect TMON for MQSeries from all monitored queue managers.
  2. Set the system clock back.
    Note: If possible, wait until no time overlap exists before completing step 3. Otherwise, invalid summary data may result for this time interval. Additionally, TMON Report Writer batch reports may show increased activity for the hour if data collection starts immediately after setting the clock back.
  3. Use the CON (connect) line command to reconnect TMON for MQSeries to all monitored queue managers.
You cannot re-cycle WebSphere MQ; you can re-cycle TMON for MQSeries
  1. Stop TMON for MQSeries and LFS.
  2. Set the system clock back. Note: If possible, wait until no time overlap exists before completing step 3. Otherwise, invalid summary data may result for this time interval. Additionally, TMON Report Writer batch reports may show increased activity for the hour if data collection starts immediately after setting the clock back.
  3. Start TMON for MQSeries and LFS.
You can re-cycle WebSphere MQ; you cannot re-cycle TMON for MQSeries
  1. Shut down WebSphere MQ.
  2. Set the system clock back.
    Note: If possible, wait until no time overlap exists before completing step 3. Otherwise, invalid summary data may result for this time interval. Additionally, TMON Report Writer batch reports may show increased activity for the hour if data collection starts immediately after setting the clock back.
  3. Start WebSphere MQ.
You can re-cycle both WebSphere MQ and TMON for MQSeries
  1. Shut down WebSphere MQ.
  2. Shut down TMON for MQSeries and LFS.
  3. Set the system clock back.
    Note: If possible, wait until no time overlap exists before completing step 4. Otherwise, invalid summary data may result for this time interval. Additionally, TMON Report Writer batch reports may show increased activity for the hour if data collection starts immediately after setting the clock back.
  4. Start TMON for MQSeries and LFS.
  5. Start WebSphere MQ.