- Symantec Endpoint Protection 11.x will keep 3 definition sets at any time: the current set and the last 2.
- Symantec Antivirus 8.x/9.x/10.x will keep 2 definition sets: the current set and the last used.
- Symantec End Point Protection 12.1.x will keep 1 set of definations.
If you see more defination being stored..... that would be cause the definations are corrupted.
I would suggest you to stop the smc services of the client and delete the definations and then monitor the issue. I am sure this would help.
From this locaiton that you have provided about virus defs.... >> C:\Program Files\Common Files\Symantec Shared\VirusDefs
This is the locaiton for 11.0.x client.
You could also refer to below article
Drive Space used by Virus Definitions Updates
Article URL http://www.symantec.com/docs/TECH141811