Database management is an essential task which should be performed properly in any enterprise environment. Most of the business oriented people prefer MS SQL database for efficient management of data. It stores huge amount of data in secured manner and offers easy accessibility. You can perform various operations on your data with the help of query languages and varieties of command. It offers you facility to set the SQL server database online or offline so that different users can easily modify and access the database depending upon the privileges. Due to this facility SQL is highly preferred for any official database management system.

But at times it happens that SQL ‘Alter Database mydb Set Online’ command fails to set the database online and you are unable to perform the operations. It has been that most of the SQL users face below error messages while setting SQL server database online.

Msg 5171, Level 16, State 1, Line 1 E:\Data\mydb_log.ldf is not a primary database file. Msg 5171, Level 16, State 2, Line 1 E:\Data\mydb.mdf is not a primary database file. File activation failure. The physical file name "E:\Data\mydb.mdf" may be incorrect.

Msg 945, Level 14, State 2, Line 1 Database 'mydb' cannot be opened due to inaccessible files or insufficient memory or disk space. See the SQL Server errorlog for details. Msg 5069, Level 16, State 1, Line 1 ALTER DATABASE statement failed.

Once the error appears you are unable to set the SQL server database online. Usually SQL error appears due to damaged database and above problem is also the result of same. The major reason behind the occurrence of this error message is corrupt MDF files which get corrupted due to various adverse reasons like as:

• Improper shut down of system
• Corrupt SQL index
• Damaged file header
• Malfunctioning of application
• Virus infection

When the MDF file gets corrupted it becomes inaccessible and SQL server is unable to read its data. So, you are unable to set the SQL server database online. In order to resolve this problem you can repair your damaged database using DBCC CHECKDB utility. If this tool fails to repair the damage you can use MS SQL Database Repair Software. It safely repairs and restores SQL database. It works very well on every versions of SQL.