Commvault: UpdateIndex index processing failed

 Issue Description: 

The backup copy of VMware VM backup in Commvault reported failure. The backup jobs failed with the following error: 

     Error Code: [14:21]

    Description: UpdateIndex index processing failed for     

Resolution: 

Login to the proxy VM and review the updateindex.log and search for the string 'FATAL ERROR' 

UPDATEINDEX FATAL ERROR: extent size change detected for vm. 

When the VM extent size changes, Commvault incremental backup fails to run. The way to fix the issue is to run a FULL backup and then attempt an incremental backup.