Hi Santosh,
Thank you for posting in Symantec community.
I would be glad to answer your query.
Following article should answer your all queries.
https://www-secure.symantec.com/connect/articles/how-manage-sepm-121-database
Q.On what period the backup was taken and what are methods.
--> SEPM database maintenance runs only at midnight. From the Admin page we've got the Back Up Database Now option and from the Start Menu > SEPM Tools, we can back up the database from there too.
Q.Can it possible to take backup online and periodically on remote databse/server.
--> We can see the backup path. This isn't editable. This is the only location where the backup is stored, so you need to make sure that's the location that's being backed up and taken offsite. You can choose the number of backups to keep in this location. We can back up logs as well if you wish, that will obviously make the backup larger, and we have the Schedule Settings.
To back up an embedded database from the SEPM console, in the SEPM console, click Admin. On the Admin page, click Servers and under View, click the icon that represents the embedded database.
Under Tasks, click Edit Backup Settings.
In the Backup Settings for Local Site dialog box, mark the Schedule Backups checkbox and specify the backup schedule.
The backup is placed in a zip file labeled with the date on which the backup occurs.
Q. How the failure to SEPM can be recovered.
Article: Symantec Endpoint Protection 12.1: Best Practices for Disaster Recovery with the Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH160736
Q. What state of syatem/application DB needs to be protected and Backuped for futured recovery.
--> By default, SEPM database maintenance runs only at midnight and it will not run when the SEPM service is restarted.
Symantec Endpoint Protection Manager: How is Database Maintenance scheduled?
http://www.symantec.com/docs/TECH95880
Best Practices to Backing up a Microsoft SQL Database on Demand from the Symantec Endpoint Protection Manager Console
http://www.symantec.com/docs/TECH96409