Disk group has used % of safely usable free space

OEM Alert Message looks like;

Message=Disk group DISGKGROUP_FLASH_01 has used 75.08% of safely usable free space. Metric=Disk Group Used % of Safely Usable Metric value=75.08 Disk Group Name=DISGKGROUP_FLASH_01 Severity=Warning Target Name=+ASM1_DBSRVR.siva.com Target type=Automatic Storage Management Host=dbsrvr.siva.com Occurred At=Sep 29, 2011 11:14:52 PM IST Acknowledged=No Notification Rule Name=DBSrvr ASM Health Check Notification Rule Owner=DBA

 

By default:
This metric will generate a warning alert if the Disk Group is using 90% of the Safely usable space and
Critical warning for 100 %. Threshold limit can be changed to generate alert at different values.

This metric is collected at a time interval of 15 minutes.

Metric Collection:
This metric is collected from the view V$ASM_DISKGROUP_STAT

Used % of Safely Usable = 100 - (usable_file_mb/usable_total_mb)*100 Where usable_total_mb = total_mb - required_mirror_free_mb)/redundancy_factor

total_mb and required_mirror_free_mb will come from the V$ASM_DISKGROUP_STAT  view column and

Redundancy Factor	Disk Group Type
1	External
2	Normal
3	High

Query:

select 100-(FREE_MB/TOTAL_MB)*100 as "Used % Safely Usable Area",  Name from v$asm_diskgroup_stat

Alternatively connect to ASM and check the free space;

ASMCMD> lsdg

Workaround:
If the Archive Log file occupies the ASM Disk group, move the files or delete files to free up Disk group.

Permanent Resolution:
New disks can be added in a disk group to avoid the alerts.
Go to the Disk Group general page ---> and click on add button to add a new disk to a disk group.