Policies can be scheduled, unscheduled, and executed on demand. A policy run scans the pair’s path, then moves the files that satisfy the criteria for the move. While policy runs are in progress, performance is slower. It is best to schedule policy runs in off-peak hours so that the user experience is not adversely affected.
Multiple policies can be scheduled to run at the same time. The policies are grouped for the run according to the direction files are to be moved: Primary to Secondary, then Secondary to Primary. When policies are run in combination, a file is moved if its conditions meet the rules defined in any one of the policies. That is, the different policies are enforced with an OR condition. The rules within an individual policy are enforced as an AND condition.
Only one scanning action can be performed on a pair at any given time. Actions include the following:
Running one or more policies on a pair.
Previewing one or more policies on a pair by doing a test run that reports what files would be moved if the policy were enforced at that time.
Scanning the pair to collect file statistics for the pair history. The history scan runs once daily by default. You can set it to run hourly or weekly. For information, see Section 8.10, Scheduling the Pair History Scan.
Dynamic File Services does not queue the requests for activities. If the pair is busy, the pending action might not run.
For interval-based policies, the policy can start whenever the pair is available during the specified interval. If the pair is busy at the beginning of the interval, the pending action retries to start itself until the end of the interval. After it starts, the policy runs until complete, or until the end of the interval, depending on which event occurs first.
For policies that begin at a given start time and run until complete, if the pair is busy at the scheduled start time, the pending action retries to start itself for up to 20 minutes beyond the scheduled start time. If you schedule the policies to start at the same time, they can run concurrently. If you schedule policies to begin at different times, there must be sufficient time available for one policy to complete before another is scheduled to begin.
For example, if PolicyA and PolicyB are scheduled to run on the same pair at 12:00 a.m. and 12:05 a.m. respectively, and each policy takes 30 minutes to complete, PolicyB probably never runs. However, if you schedule the two policies to start at the same time, both policies are run in combination.
To avoid scheduling conflicts, we recommend that you use one of the following approaches when scheduling policies for a pair:
Same Schedule: Schedule the pair’s assigned policies to start and stop at the same time. This allows the Standard Policy engine to run them concurrently, which is the most efficient way to enforce policies. Policies can be run manually at other times if needed.
Non-Overlapping Schedule: Schedule the pair’s policies so that each policy runs in its own window of time, making sure that the start times and stop times do not overlap. Policies can be run manually as needed at unscheduled times. This approach makes it more difficult to predict idle times to run policies manually on the pair.
For information about how scheduling works, see Section 10.4.1, Understanding How Changes Affect the Scheduled Run Interval.