How to repair SQL Server system database?

Sorry no clues.

Some useful information can be found here - Repair SQL Database File via SQL Server Management Studio

The author has explained an easy manual trick to fix corrupt SQL database file. It might be helpful here.

Thanks.

Take a look at this link, may be this will help you out: http://sqltechtips.blogspot.com/2015/12/fcb-open-failed-error-17204.html 

If you find database is corrupted then you can take the help of third party tool to recover repair your database: http://www.sqlrecoverysoftware.net/sql-server-mdf-file/ 

In order to fix damaged or corrupted SQL Database, professionals recommend using tools like SQL Database Recovery.

SQL Database Recovery tool is specifically designed to recover data from even severely corrupted SQL files and this tool even lets you recover all the data from SQL server like ables, views, triggers, default etc.

This tool lets users preview the recovered data before saving and the tool is compatible with all types of SQL databases.

To learn more about this tool, visit: https://www.sysinfotools.com/recovery/ms-sql-database-recovery.php

There are many reasons which can cause corruption in SQL database. If the MDF file is tagged as suspect, you can try an easy manual trick here. The manual trick doesn't require any 3rd party tool. All you need to use is Microsoft SQL Server Management Studio and a couple of database console commands (DBCCs): DBCC CHECKDB and DBCC DBREPAIR. Refer to this article to know how to repair SQL database manually - How to Restore SQL Database Objects from Corrupt MDF File?

You can start with primary ways to repair SQL database. The basic method for minor corruption issues include: **REPAIR_REBUILD:**. For this, SET your SQL database in single user mode. Then, Database_name GO ALTER DATABASE Database_name SET SINGLE_USER GO DBCC CHECKDB(‘Database_name’,REPAIR_REBUILD) GO **REPAIR_ALLOW_DATA_LOSS:** .

If method of using repair build option does not work. You can try this alternative option using command- DBCC CHECKDB (‘Database_name’, REPAIR_ALLOW_DATA_LOSS). In case of no successful SQL recovery using above ways, you can opt for secure and quick SQL repair tool like [Stellar Phoenix SQL database repair] which has been reviewed by MVP's to repair the severely corrupt SQL server MDF and NDF database files.

Checkout this blog post. Step by step guide to repair SQL Server Database. Read carefully and do it yourself.

Steps to Repair SQL Server MDF File When DBCC CHECKDB Fails | Exchange Server Helping Tips .

Thanks