Hi,
Thanks for the update.
Firts upgrade SEPM can refer the following article:
https://www-secure.symantec.com/connect/articles/sep-11x-sep-121-upgrade-process-graphical-overview
http://www.symantec.com/docs/TECH211821
Points to remember prior to upgrade
1) Backup the database and server private key folder to stay on safer side
2) The SEP 12.1 SEPM upgrade installer requires three times the current database size (sem5.db) if upgrading from pre-12.1 SEPM with the embedded database only. Make sure sufficient free space is available before upgrade.
After successful SEPM upgrade plan for SEP client upgrade.
Upgrade clients to SEP 12.1 by Auto upgrade feature
https://www-secure.symantec.com/connect/articles/sepm-121-auto-upgrade
Note: SEP 12.1 employs a side-by-side, replace on reboot installation strategy. Side-by-side means that new files are written to a new folder, referred to as a silo, isolated from the existing operational folder. Because the two versions are separated from each other, during a migration the older software is left running unchanged until the next reboot.
The primary benefit of side-by-side installation and replace on reboot is that the system continues to be protected by the existing software until the new version is in operation after the reboot.
This technique enables you to change the normal portion of the installation path during a migration, when applicable.