SQL Server 2008 Service fails to start after Service Pack Installation

Some times you may find that the SQL Server Service is not starting after applying a service pack and when you check in the Event Viewer you find the below message.

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.

SQL Server Setup creates a database with the data file name temp_MS_AgentSigningCertificate_Database.mdf  during the installation process and if the SQL Server setup is not able to create that database in the default data path then the above error is returned as it is not able to find the path.
To fix this issue.


Go to Registry editor,  ->To open this, ->go to “Run” and type -> “regedit” and click “ok”


First go to this path and make sure that the path in the key SQLDataRoot exists. If not then give a valid path to this key.
HKEY_LOCAL_MACHINESOFTWAREMicrosoftMicrosoft SQL ServerMSSQL10.<instance name>Setup3

Then go to this path and make sure that the path in the keys “BackupDirectory”, “DefaultData” and “DefaultLog” exists. If not then give a valid path to these keys.
HKEY_LOCAL_MACHINESOFTWAREMicrosoftMicrosoft SQL ServerMSSQL10.<instance name>MSSQLServer


Now you should be able to start the SQL Server Service without any issues.
Once the Service is started, verify the SQL Server, databases and others to make sure everything is fine.

Also verify if the Service pack or the CU is installed correctly.