If you rebuild your system databases without making any backup copies, you will lose your logins and jobs. However, since you have to reset all of your data in the database, you must first ensure having system database backups. Rebuild operation resets the system databases and allows the instance to be online without any error. In this case, it is necessary to rebuild the system databases.

Sometimes, you cannot start a SQL Server instance because a system database (or some of them) is corrupted. This article explores the process for rebuilding system databases – Master, MSDB, and Model for SQL Server on Linux and Windows. 79707 : New backup request received for Client, iDataAgent, Instance, Subclient, Backup Level.79711 : Query Result Cannot back up the log of the master database.Error: Cannot back up the log of the master database. 79712 : Error encountered during backup.Client, Agent Type, Subclient, Backup Level, Objects, Failed, Duration, Total Size, Media or Mount Path Used. Job Options:Create new index, Start new media, Backup all subclients, Truncation Log, Follow mount points, Backup files protected by system file protection, Stop DHCP service when backing up system state data, Stop WINS service when backing up system state data

ERROR CODE : Error encountered during backup.

You can do this by nominating NOT to back it up in the primary copy for the SQL data agent'

Typically the master database is just a template and is not used by any applications (applications that do require the use of an SQL database create their own) so there should be no harm in preventing it from being backed up If this is happening intermittently its possible that something is locking the transaction log, preventing SQL iData agent from accessing the log. 'The message is caused by Commvault’s inability to backup the master database’s transaction log. I have been advise by Commvault partner support to turn off the backup of the master database as the backup failed due to the log file being lock.

Restore master db