Hello,
What version of SEP are you running?
Please Follow the steps provided in the Article below:
Issue Related to Low disk space.
https://www-secure.symantec.com/connect/articles/issue-related-low-disk-space
It is also recommended to Follow the Articles Below as per the Issue:
1) Disk Space Management procedures for the Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH96214
2) Symantec Endpoint Protection virus definition folder consumes a large amount of disk space
http://www.symantec.com/docs/TECH102927
3) Best Practices for configuring the number of content revisions to keep in Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH92225
Hope this Helps in Resolving your Issue.