DOCUMENTATION: How to delete Unified Log files to reclaim disk space on the file system.
http://seer.entsupport.symantec.com/docs/279339.htm
DOCUMENTATION: How to configure Veritas NetBackup (tm) 6.x to write Unified and\or Legacy log files to a different directory
http://seer.entsupport.symantec.com/docs/281360.htm
DOCUMENTATION: Best Practice recommendations for enabling and gathering NetBackup (tm) logging
http://seer.entsupport.symantec.com/docs/282865.htm
DOCUMENTATION: How to configure automatic cleanup and recycling of unified log files with Veritas NetBackup (tm) 6.0/6.5
http://seer.entsupport.symantec.com/docs/279590.htm
They should certainly help!