Once you set a time frame, no amount of coaxing will make the clients perform their update immediately. This is because when a schedule is defined, the SEPM assigns a specific time for the client to update. The client will wait until that time has passed before requesting the update.
Working example:
8:00 AM
- You assign an update policy for your clients that tells them to update between 6 PM and 6 AM.
8:05 AM
- Your clients check in (lets say you have 2 clients)
- The client sees there is an update available and requests it from the SEPM.
- The SEPM assigns a time between 6 PM and 6 AM for each client to check-in.
- Client1 @ 6 PM, Client2 @ 12 AM (midnight)
6:01 PM
- Both clients check in.
- Client1 downloads and installs the package.
- Client2 checks in and continues to wait for 12:00 AM.
6:02 PM
- Impatient admin checks Client2, sees it hasn't updated yet and clicks "Update Content"
- Client2 checks in, sees it hasn't reached its scheduled update time and continues waiting
6:04 PM
- Impatient admin decides to call it a night and shuts down Client2.
Next day, 8:00 AM
- Client2 gets turned back on, sees that it's passed it's assigned update time and requests the update from the SEPM again
- SEPM checks the update schedule and assigns a new time to Client2... 6:00 PM
6:03 PM
- Client 2 checks in, sees it has reached its scheduled update time, downloads the update and installs it
The SEPM has an algorithm for update schedules that spreads updates over the time period for updates. This keeps the SEPM from getting slammed with requests when there are lots of clients. It also can be troublesome because it will usually distribute small numbers of clients evenly over large periods of time.