I have been working with NetBackup since 6.5 as a consultant and from time to time I have seen flat file windows backups fail with 156 errors, which is a snapshot failure. A snapshot is not typically used when doing these types of backups. To avoid these failures do the following;
Admin console > Host Properties > Master Servers > Client Attributes > Add Client (short of FQDN - however seen in netbackup) > TAB Windows Open File Backup > Snapshot error control > SELECT disable snapshot and continue
BE SURE TO DOUBLE CHECK SNAPSHOTS ARE NOT CONFIGURED FOR THIS CLIENT ON OTHER POLICIES BEFORE MAKING THIS CHANGE -- for example: if doing a windows backup for the operating system and a snapshot\backup of the Exchange database on that same server.
Hope this helps!
