The EMM server runs on the master server and I believe contains the database for backup images, media, and storage devices.
The impact is obviously bad if the EMM server goes down.
The 1st thing to do is stop and restart all Netbackup services and pray that Netbackup starts up again.
If /opt/openv is full, then free up some space. The catalog might be corrupted and in need of some cleaning up.
Any issues dealing with the catalog, I recommend calling Symantec for their expert advice.