How to restore MSDB database
If your msdb goes suspect then you have two choices, if you have backup of database then restore it else you have to recreate it
If you want to recreate it here are the steps to do it
1. Start the server with trace flag 3608.Detach the damaged msdb.
2. Navigating to the directory ‘C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Binn’ and start sqlservr.exe -c -T3608
3. Move or rename the damaged msdb files
4. Go to the folder ‘C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Install’ and run the instmsdb file.
5. Restart SQL Server without the 3608 trace flag
Lets SQL 