I have just installed SQL Server 2008 R2 SP3 and after installing it and trying to start the SQL Server instance again, it won't come online. In the SQL Server error log I can see that the following is logged:
2014-10-20 16:51:13.04 spid8s MODIFY FILE failed. File 'MSDBLog' does not exist. 2014-10-20 16:51:13.04 spid8s Error: 912, Severity: 21, State: 2. 2014-10-20 16:51:13.04 spid8s Script level upgrade for database 'master' failed because upgrade step 'sqlagent100_msdb_upgrade.sql' encountered error 598, state 1, severity 25. This is a serious error condition which might interfere with regular operation and the database will be taken offline. If the error happened during upgrade of the 'master' database, it will prevent the entire SQL Server instance from starting. Examine the previous errorlog entries for errors, take the appropriate corrective actions and re-start the database so that the script upgrade steps run to completion. 2014-10-20 16:51:13.04 spid8s Error: 3417, Severity: 21, State: 3. 2014-10-20 16:51:13.04 spid8s Cannot recover the master database. SQL Server is unable to run. Restore master from a full backup, repair it, or rebuild it. For more information about how to rebuild the master database, see SQL Server Books Online. 2014-10-20 16:51:13.04 spid8s SQL Trace was stopped due to server shutdown. Trace ID = '1'. This is an informational message only; no user action is required.
How can I fix the upgrade so it doesn't fail?