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Generic check for error Oracle ASM ORA-15042

Generic check for error Oracle ASM ORA-15042

Error ORA-15042 means asm cannot mount the diskgroup as some of it member disks are not visible to asm.
 
 
 
How to find which disk is missing:
 
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- Scan the asm alert log for last successful mount of that diskgroup, where it will list out the disks with which it was mounted. Search for below keyword
 
SUCCESS: diskgroup <diskgroup name> was mounted
 
 
 
- After that point to till issue time scan in asm alert log that what are the disks added and dropped.
 
- Finally, make a list of disk path and name which were member of diskgroup before issue occurred.
 
 
 
Diagnosis:
 
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- Check all disks permission (660) and ownership are correct. Owner/Group should be grid:asmsdmin (asmadminis SS_ASM_GRP in $GRID_HOME/rdbms/lib/config.c)
 
- Check the disks are accessible as grid os user , like:
 
dd if=<path to asm disk> of=/tmp/<devicename>.dd bs=1048576 count=10
 
- If multipath is in use , then check if the multipath base devices are presented fine.
 
 
 
Possible cause:
 
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1. Permission of disks are not correct
 
2. Disk assessed by asm is available but its base device is not available
 
3. Duplicate device is found for same disk.
 
4. Partition of the disk was modified , so that the asm disk header is not located now at 1st 4k block of starting of disk.
 
5. At least 1st 4k block data information is erases externally , that is outside of oracle
 
6. In case of asmlib , multipath disks are visible but the asmlib disks are not visible.
 
 
 
Solution
 
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1. Correct the permission
 
2. Ask you system admin to present the base device
 
3. Check with system admin that why more than 2 paths are showing for same asm disk , which are getting diskcovered by asm.
 
4. Check with system admin to correct the partition table so that it will point to correct location of asm disk header.
 
5. If only asm disk header is corrupted / wiped out and remain asm metadata is correct , then it be repaired , please raise SR with oracle support. Otherwise you need to recreate the diskgroup.
 
6.
 
- Check the label is present by running below command
 
kfed read /dev/oracleasm/disks/<label name>| grep kfdhdb.driver.provstr
 
- ASMLIB drivers are loaded
 
- ASMLIB configuration file /etc/sysconfig/oracleasm is having proper entry
 
 
 
 
 
 Also, please check the following document:
 
 
 
=)> ORA-15063 / ORA-15042 - TROUBLESHOOTING STEPS BEFORE OPENING a SR to Oracle Support (Doc ID 1535996.1)