Hi Kamal,
This alarm indicates that you disk i getting full.
This is the first alarm that youĀ“re going to receive, if you donĀ“t take no actions you will start to receive "HighWater" alarms, when receiving this, the system will start to delete files on Log Partition, to avoid disk be complete full.
Check the trace/logs configuration on Cisco Unfied Serviceability, there you can control the number o trace files and size that server can store. Also perform a clean up on disk for unused trace/log files using RTMT.
Detailed information:
http://cisco.sitecelerate.com/en/US/docs/voice_ip_comm/cucm/managed_services/cucm_health.html
Regards