How to: Add New Database Files
You can expand a database by creating a new database file in the database.
Note
You must always make a backup of the database before you expand it. For more information, see Create a Full Database Backup (SQL Server).
To add a new database file
In the development environment, on the File menu, choose Database, and then choose Alter. The Alter Database window opens.
Choose the Database Files tab.
Select the first empty line in the window.
In the Logical Name field, enter a logical name for each database file.
In the File Name field, enter the full path and name of the database file.
Note
We recommend that primary database files have the file name extension .mdf and that secondary database files have the file name extension .ndf. The first data file that is listed is the primary file.
In the Size (MB) field, enter the initial size in megabytes of the database file.
In the File Growth field, enter the amount by which the database file will increase every time that it expands. This can be expressed in kilobytes (KB), megabytes (MB) or as a percentage (%).The default value is MB.
However, if you enter the value in megabytes, SQL Server will convert it to kilobytes. If you enter the value as a percentage, SQL Server will display it as a percentage.
Select the Unrestricted Growth check box if you want SQL Server to expand the database file when it must.
In the Maximum size (MB) field, enter the maximum size to which the database file can grow.
You can either allow the database file to grow without restriction or you must specify a maximum file size. If you do not specify a maximum size, SQL Server will expand the database file as often as necessary. This expansion is limited only by the available disk space.