Using SYNCVAL in a policy to specify the time of day that a check runs

You can use the SYNCVAL parameter in a policy to give you more control over when a check runs, or at least when it is scheduled to run. Because SYNCVAL, INTERVAL, and EXCEPTINTERVAL all work together, you must coordinate the values. SYNCVAL lets you specify when a check is scheduled to run, while INTERVAL and EXCEPTINTERVAL specify how often it runs, synchronized with the SYNCVAL parameter.

You might find SYNCVAL useful to schedule check workload for a low-stess time like overnight maintenance windows, to schedule checks for specific times in order to balance the overall system workload, or maybe you simply have a check that you want to run very very predictably.

Note that:

You can only use SYNCVAL in a policy statement - it is valid only on an ADD|ADDREPLACE, POLICY STMT(statement_name) UPDATE,filters,update_options statement in the update_options.
You can use INTERVAL and EXCEPTINTERVAL on either the :
- UPDATE or ADD|ADDREPLACE,POLICY STMT with UPDATE
- ADD/ADDREPLACE ,CHECK statement

The syntax for SYNCVAL is:

SYNCVAL={SYSTEM|hh:mm|*:mm)

For the full syntax, see Syntax and parameters for HZSPRMxx and MODIFY hzsproc.

The way you specify SYNCVAL changes the way the system measures the INTERVAL for a check:

If you specify or default to SYSTEM, nothing changes. The check runs immediately after being added, and subsequently thereafter at the interval defined for the check. The specified interval time starts ticking away when a check finishes running.
If you specify SYNCVAL=(hh:mm | *:mm, you are specifying the time of day at which the check is scheduled to run. Then the INTERVAL or EINTERVAL specify how often. When you specify SYNCVAL=(hh:mm | *:mm), the interval time starts ticking when the check starts running (not when it finishes).
The INTERVAL | EINTERVAL you specify interacts with SYNCVAL as follows:
- If the INTERVAL is 24 hours, the check is scheduled to run at the SYNCVAL time of day, every day.
- If the INTERVAL is less than 24 hours, the check is scheduled to run multiple times per day as specified by the INTERVAL, and one of those times is the SYNCVAL time of day. Thus you are using the SYNCVAL time to synchronize the check interval.
- If the INTERVAL is greater than 24 hours, the check does not run every day, honoring the INTERVAL, but when it is scheduled to run, it will be at the SYNCVAL time of day.