How to enable client to take the updates from SEPM Server only and not from Internet.
What is the configuration done in your live update policy?
You can set "Use the default management server" to Downloads the updates from the Symantec Endpoint Protection Manager,
https://www-secure.symantec.com/connect/articles/configure-liveupdate-run-symantec-endpoint-protection-manager-sepm-part-2
Make the following change to the LiveUpdate policy: Policies > LiveUpdate > LiveUpdate Settings policy > Edit the policy By default, "Use the default management server (recommended)" is checked,uncheck "Use default Symantec LiveUpdate server
Log in an go to Policies >> LiveUpdate
Select your specific policy and edit it accordingly.
On Server Settings tab make sure to check the box for "Use the default management server"
Uncheck the other and Click Ok.
In your LiveUpdate policy, under Server Settings, unchecl "Use a LiveUpdate server" and only ensure "Use the default management server" is checked.
Now update is from default management server only...
How to configure client to take update from server at fixed time period. As i see no option on this.
There no option available.
Once SEPM will update virus defination,SEP client automatic update next heart beat setting.
You can adjust the schedule that Symantec Endpoint Protection Manager uses to download content updates from LiveUpdate to the management server. For example, you can change the default server schedule frequency from hourly to daily to save bandwidth.
See as per below Mithun comments
https://www-secure.symantec.com/connect/forums/system-running-slow#comment-6556331
There is not be anyo of the option that where you can schedule the client to take the update on the respective time period. As you can set the server to take the download from symantec server on scheduled time.
Below of the thread guide you
https://www-secure.symantec.com/connect/forums/scheduling-updates-symantec-endpoint-protection-manager