Exchange 2013 Database Content Index State

Hello,

The content Index State of all my Exchange 2013 databases are Unknown some timesFailed or FailedandSuspended. I have troubleshooted by deleting and rebuilding the Catalog folder, Which works for only a while on some databases and on the others no effect even shows up.

I have a DAG configured.

Please can any one help me explain the cause, or if  i had a misconfiguration some where some how. Kindly Need to know the Cause before i now look at any advanced troubleshooting.

Thanks & Regards,

Ronald