HI,

The Rx4DefsSEP would not work for SEP 12.1.

I would suggest you to use the .jdb file as of now to update the definitions on SEPM as well as clients.

Check these Articles:

How to update definitions for Symantec Endpoint Protection Manager (SEPM) using a .jdb file

http://www.symantec.com/docs/TECH102607

How to manually update definitions for a managed Symantec Endpoint Protection Client using the .jdb file

http://www.symantec.com/docs/TECH104363

Also, check this Downloads

Script to download Definitions from SEPM

NOTE: These script is not provided nor supported by Symantec.

Check this thread

https://www-secure.symantec.com/connect/forums/best-way-remotely-repair-clients-corrupted-definitions

The Rx4DefsSEP do not work for SEP 12.1.

How to update definitions for Symantec Endpoint Protection Manager (SEPM) using a .jdb file

http://www.symantec.com/docs/TECH102607

How to manually update definitions for a managed Symantec Endpoint Protection Client using the .jdb file

http://www.symantec.com/docs/TECH104363

Also, check this Downloads

Script to download Definitions from SEPM (Not supported by Symantec)

https://www-secure.symantec.com/connect/forums/best-way-remotely-repair-clients-corrupted-definitions