I have 3 archive servers....I am getting these errors in one of my archive server logs.....  The servers have been up for days with out any downtime... how can i trouble shoot the communication link failure occurred when accessing the database server error?

Replication of vault "PDM" failed.

Cause: IDispatch error #103

"A communication link failure occurred when accessing the database server. The database service might have been restarted or the network might have gone down. Please try the operation again and contact your system administrator if the problem persists."

Could not run cleaner service on vault PDM.

Details:

Failed to get documents to clean from database.