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ALTER DATABASE File and Filegroup Options (Transact-SQL)

Modifies the files and filegroups associated with the database. Adds or removes files and filegroups from a database, changes the attributes of a database or its files and filegroups. For other ALTER DATABASE options, see ALTER DATABASE (Transact-SQL).

Topic link iconTransact-SQL Syntax Conventions


ALTER DATABASE database_name 
{
    <add_or_modify_files>
  | <add_or_modify_filegroups>
}
[;]

<add_or_modify_files>::=
{
    ADD FILE <filespec> [ ,...n ] 
        [ TO FILEGROUP { filegroup_name } ]
  | ADD LOG FILE <filespec> [ ,...n ] 
  | REMOVE FILE logical_file_name 
  | MODIFY FILE <filespec>
}

<filespec>::= (
    NAME =logical_file_name  
    [ , NEWNAME =new_logical_name ] 
    [ , FILENAME = {'os_file_name' | 'filestream_path' } ] 
    [ , SIZE =size [ KB | MB | GB | TB ] ] 
    [ , MAXSIZE = { max_size [ KB | MB | GB | TB ] | UNLIMITED } ] 
    [ , FILEGROWTH =growth_increment [ KB | MB | GB | TB| % ] ] 
    [ , OFFLINE ]
)<add_or_modify_filegroups>::=
{
    | ADD FILEGROUP filegroup_name 
        [ CONTAINS FILESTREAM ]
    | REMOVE FILEGROUP filegroup_name 
    | MODIFY FILEGROUP filegroup_name
        { <filegroup_updatability_option> 
        | DEFAULT
        | NAME =new_filegroup_name 
        }
}
<filegroup_updatability_option>::=
{
    { READONLY | READWRITE } 
    | { READ_ONLY | READ_WRITE }
}

<add_or_modify_files>::=

Specifies the file to be added, removed, or modified.

database_name

Is the name of the database to be modified.

ADD FILE

Adds a file to the database.

TO FILEGROUP { filegroup_name }

Specifies the filegroup to which to add the specified file. To display the current filegroups and which filegroup is the current default, use the sys.filegroups catalog view.

ADD LOG FILE

Adds a log file be added to the specified database.

REMOVE FILE logical_file_name

Removes the logical file description from an instance of SQL Server and deletes the physical file. The file cannot be removed unless it is empty.

logical_file_name

Is the logical name used in SQL Server when referencing the file.

MODIFY FILE

Specifies the file that should be modified. Only one <filespec> property can be changed at a time. NAME must always be specified in the <filespec> to identify the file to be modified. If SIZE is specified, the new size must be larger than the current file size.

To modify the logical name of a data file or log file, specify the logical file name to be renamed in the NAME clause, and specify the new logical name for the file in the NEWNAME clause. For example:

MODIFY FILE ( NAME = logical_file_name, NEWNAME = new_logical_name ) 

To move a data file or log file to a new location, specify the current logical file name in the NAME clause and specify the new path and operating system file name in the FILENAME clause. For example:

MODIFY FILE ( NAME = logical_file_name, FILENAME = ' new_path/os_file_name ' )

When you move a full-text catalog, specify only the new path in the FILENAME clause. Do not specify the operating-system file name.

For more information, see Moving Database Files.

For a FILESTREAM filegroup, NAME can be modified online. FILENAME can be modified online; however, the change does not take effect until after the container is physically relocated and the server is shutdown and then restarted.

You can set a FILESTREAM file to OFFLINE. When a FILESTREAM file is offline, its parent filegroup will be internally marked as offline; therefore, all access to FILESTREAM data within that filegroup will fail.

<filespec>::=

Controls the file properties.

NAME logical_file_name

Specifies the logical name of the file.

logical_file_name

Is the logical name used in an instance of SQL Server when referencing the file.

NEWNAME new_logical_file_name

Specifies a new logical name for the file.

new_logical_file_name

Is the name to replace the existing logical file name. The name must be unique within the database and comply with the rules for identifiers. The name can be a character or Unicode constant, a regular identifier, or a delimited identifier. For more information, see Using Identifiers As Object Names.

FILENAME { 'os_file_name' | 'filestream_path' }

Specifies the operating system (physical) file name.

' os_file_name '

For a standard (ROWS) filegroup, this is the path and file name that is used by the operating system when you create the file. The file must reside on the server on which SQL Server is installed. The specified path must exist before executing the ALTER DATABASE statement.

SIZE, MAXSIZE, and FILEGROWTH parameters cannot be set when a UNC path is specified for the file.

Data files should not be put on compressed file systems unless the files are read-only secondary files, or if the database is read-only. Log files should never be put on compressed file systems. For more information, see Read-Only Filegroups and Compression.

If the file is on a raw partition, os_file_name must specify only the drive letter of an existing raw partition. Only one file can be put on each raw partition.

'filestream_path'

For a FILESTREAM filegroup, FILENAME refers to a path where FILESTREAM data will be stored. The path up to the last folder must exist, and the last folder must not exist. For example, if you specify the path C:\MyFiles\MyFilestreamData, C:\MyFiles must exist before you run ALTER DATABASE, but the MyFilestreamData folder must not exist.

The filegroup and file (<filespec>) must be created in the same statement. There can be only one file, <filespec>, for a FILESTREAM filegroup.

The SIZE, MAXSIZE, and FILEGROWTH properties do not apply to a FILESTREAM filegroup.

SIZE size

Specifies the file size. SIZE does not apply to FILESTREAM filegroups.

size

Is the size of the file.

When specified with ADD FILE, size is the initial size for the file. When specified with MODIFY FILE, size is the new size for the file, and must be larger than the current file size.

When size is not supplied for the primary file, the SQL Server uses the size of the primary file in the model database. When a secondary data file or log file is specified but size is not specified for the file, the Database Engine makes the file 1 MB.

The KB, MB, GB, and TB suffixes can be used to specify kilobytes, megabytes, gigabytes, or terabytes. The default is MB. Specify a whole number and do not include a decimal. To specify a fraction of a megabyte, convert the value to kilobytes by multiplying the number by 1024. For example, specify 1536 KB instead of 1.5 MB (1.5 x 1024 = 1536).

MAXSIZE { max_size| UNLIMITED }

Specifies the maximum file size to which the file can grow. MAXSIZE does not apply to FILESTREAM filegroups.

max_size

Is the maximum file size. The KB, MB, GB, and TB suffixes can be used to specify kilobytes, megabytes, gigabytes, or terabytes. The default is MB. Specify a whole number and do not include a decimal. If max_size is not specified, the file size will increase until the disk is full.

UNLIMITED

Specifies that the file grows until the disk is full. In SQL Server, a log file specified with unlimited growth has a maximum size of 2 TB, and a data file has a maximum size of 16 TB.

FILEGROWTH growth_increment

Specifies the automatic growth increment of the file. The FILEGROWTH setting for a file cannot exceed the MAXSIZE setting. FILEGROWTH does not apply to FILESTREAM filegroups.

growth_increment

Is the amount of space added to the file every time new space is required.

The value can be specified in MB, KB, GB, TB, or percent (%). If a number is specified without an MB, KB, or % suffix, the default is MB. When % is specified, the growth increment size is the specified percentage of the size of the file at the time the increment occurs. The size specified is rounded to the nearest 64 KB.

A value of 0 indicates that automatic growth is set to off and no additional space is allowed.

If FILEGROWTH is not specified, the default value is 1 MB for data files and 10% for log files, and the minimum value is 64 KB.

NoteNote

Starting in SQL Server 2005, the default growth increment for data files has changed from 10% to 1 MB. The log file default of 10% remains unchanged.

OFFLINE

Sets the file offline and makes all objects in the filegroup inaccessible.

Caution noteCaution

Use this option only when the file is corrupted and can be restored. A file set to OFFLINE can only be set online by restoring the file from backup. For more information about restoring a single file, see RESTORE (Transact-SQL).

<add_or_modify_filegroups>::=

Add, modify, or remove a filegroup from the database.

ADD FILEGROUP filegroup_name

Adds a filegroup to the database.

CONTAINS FILESTREAM

Specifies that the filegroup stores FILESTREAM binary large objects (BLOBs) in the file system.

REMOVE FILEGROUP filegroup_name

Removes a filegroup from the database. The filegroup cannot be removed unless it is empty. Remove all files from the filegroup first. For more information, see "REMOVE FILE logical_file_name," earlier in this topic.

MODIFY FILEGROUP filegroup_name { <filegroup_updatability_option> | DEFAULT | NAME =new_filegroup_name }

Modifies the filegroup by setting the status to READ_ONLY or READ_WRITE, making the filegroup the default filegroup for the database, or changing the filegroup name.

<filegroup_updatability_option>

Sets the read-only or read/write property to the filegroup.

DEFAULT

Changes the default database filegroup to filegroup_name. Only one filegroup in the database can be the default filegroup. For more information, see Understanding Files and Filegroups.

NAME = new_filegroup_name

Changes the filegroup name to the new_filegroup_name.

<filegroup_updatability_option>::=

Sets the read-only or read/write property to the filegroup.

READ_ONLY | READONLY

Specifies the filegroup is read-only. Updates to objects in it are not allowed. The primary filegroup cannot be made read-only. To change this state, you must have exclusive access to the database. For more information, see the SINGLE_USER clause.

Because a read-only database does not allow data modifications:

  • Automatic recovery is skipped at system startup.

  • Shrinking the database is not possible.

  • No locking occurs in read-only databases. This can cause faster query performance.

NoteNote

The keyword READONLY will be removed in a future version of MicrosoftSQL Server. Avoid using READONLY in new development work, and plan to modify applications that currently use READONLY. Use READ_ONLY instead.

READ_WRITE | READWRITE

Specifies the group is READ_WRITE. Updates are enabled for the objects in the filegroup. To change this state, you must have exclusive access to the database. For more information, see the SINGLE_USER clause.

NoteNote

The keyword READWRITE will be removed in a future version of MicrosoftSQL Server. Avoid using READWRITE in new development work, and plan to modify applications that currently use READWRITE. Use READ_WRITE instead.

The status of these options can be determined by examining the is_read_only column in the sys.databases catalog view or the Updateability property of the DATABASEPROPERTYEX function.

To decrease the size of a database, use DBCC SHRINKDATABASE.

You cannot add or remove a file while a BACKUP statement is running.

A maximum of 32,767 files and 32,767 filegroups can be specified for each database.

In SQL Server 2005 or later, the state of a database file (for example, online or offline), is maintained independently from the state of the database. For more information, see File States. The state of the files within a filegroup determines the availability of the whole filegroup. For a filegroup to be available, all files within the filegroup must be online. If a filegroup is offline, any try to access the filegroup by an SQL statement will fail with an error. When you build query plans for SELECT statements, the query optimizer avoids nonclustered indexes and indexed views that reside in offline filegroups. This enables these statements to succeed. However, if the offline filegroup contains the heap or clustered index of the target table, the SELECT statements fail. Additionally, any INSERT, UPDATE, or DELETE statement that modifies a table with any index in an offline filegroup will fail.

Moving Files

In SQL Server 2005 or later, you can move system or user-defined data and log files by specifying the new location in FILENAME. This may be useful in the following scenarios:

  • Failure recovery. For example, the database is in suspect mode or shutdown caused by hardware failure.

  • Planned relocation.

  • Relocation for scheduled disk maintenance.

For more information, see Moving Database Files.

Initializing Files

By default, data and log files are initialized by filling the files with zeros when you perform one of the following operations:

  • Create a database.

  • Add files to an existing database.

  • Increase the size of an existing file.

  • Restore a database or filegroup.

Data files can be initialized instantaneously. This enables for fast execution of these file operations. For more information, see Database File Initialization.

A. Adding a file to a database

The following example adds a 5-MB data file to the AdventureWorks database.


USE master;
GO
ALTER DATABASE AdventureWorks 
ADD FILE 
(
    NAME = Test1dat2,
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\t1dat2.ndf',
    SIZE = 5MB,
    MAXSIZE = 100MB,
    FILEGROWTH = 5MB

);
GO


B. Adding a filegroup with two files to a database

The following example creates the filegroup Test1FG1 in the AdventureWorks database and adds two 5-MB files to the filegroup.

USE master
GO
ALTER DATABASE AdventureWorks
ADD FILEGROUP Test1FG1;
GO

ALTER DATABASE AdventureWorks 
ADD FILE 
(
    NAME = test1dat3,
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\t1dat3.ndf',
    SIZE = 5MB,
    MAXSIZE = 100MB,
    FILEGROWTH = 5MB
),
(
    NAME = test1dat4,
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\t1dat4.ndf',
    SIZE = 5MB,
    MAXSIZE = 100MB,
    FILEGROWTH = 5MB
)
TO FILEGROUP Test1FG1;
GO


C. Adding two log files to a database

The following example adds two 5-MB log files to the AdventureWorks database.

USE master;
GO
ALTER DATABASE AdventureWorks 
ADD LOG FILE 
(
    NAME = test1log2,
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\test2log.ldf',
    SIZE = 5MB,
    MAXSIZE = 100MB,
    FILEGROWTH = 5MB
),
(
    NAME = test1log3,
    FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\test3log.ldf',
    SIZE = 5MB,
    MAXSIZE = 100MB,
    FILEGROWTH = 5MB
);
GO


D. Removing a file from a database

The following example removes one of the files added in example B.

USE master;
GO
ALTER DATABASE AdventureWorks
REMOVE FILE test1dat4;
GO


E. Modifying a file

The following example increases the size of one of the files added in example B.

USE master;
GO
ALTER DATABASE AdventureWorks 
MODIFY FILE
    (NAME = test1dat3,
    SIZE = 20MB);
GO


F. Moving a file to a new location

The following example moves the Test1dat2 file created in example A to a new directory.

NoteNote

You must physically move the file to the new directory before running this example. Afterward, stop and start the instance of SQL Server or take the AdventureWorks database OFFLINE and then ONLINE to implement the change.

USE master;
GO
ALTER DATABASE AdventureWorks
MODIFY FILE
(
    NAME = Test1dat2,
    FILENAME = N'c:\t1dat2.ndf'
);
GO

G. Moving tempdb to a new location

The following example moves tempdb from its current location on the disk to another disk location. Because tempdb is re-created each time the MSSQLSERVER service is started, you do not have to physically move the data and log files. The files are created when the service is restarted in step 3. Until the service is restarted, tempdb continues to function in its existing location.

  1. Determine the logical file names of the tempdb database and their current location on disk.

    SELECT name, physical_name
    FROM sys.master_files
    WHERE database_id = DB_ID('tempdb');
    GO
    
  2. Change the location of each file by using ALTER DATABASE.

    USE master;
    GO
    ALTER DATABASE tempdb 
    MODIFY FILE (NAME = tempdev, FILENAME = 'E:\SQLData\tempdb.mdf');
    GO
    ALTER DATABASE  tempdb 
    MODIFY FILE (NAME = templog, FILENAME = 'E:\SQLData\templog.ldf');
    GO
    
  3. Stop and restart the instance of SQL Server.

  4. Verify the file change.

    SELECT name, physical_name
    FROM sys.master_files
    WHERE database_id = DB_ID('tempdb');
    
  5. Delete the tempdb.mdf and templog.ldf files from their original location.

H. Making a filegroup the default

The following example makes the Test1FG1 filegroup created in example B the default filegroup. Then, the default filegroup is reset to the PRIMARY filegroup. Note that PRIMARY must be delimited by brackets or quotation marks.

USE master;
GO
ALTER DATABASE AdventureWorks 
MODIFY FILEGROUP Test1FG1 DEFAULT;
GO
ALTER DATABASE AdventureWorks 
MODIFY FILEGROUP [PRIMARY] DEFAULT;
GO


I. Adding a Filegroup Using ALTER DATABASE

The following example adds a FILEGROUP that contains the FILESTREAM clause to the FileStreamPhotoDB database.

--Create and add a FILEGROUP that CONTAINS the FILESTREAM clause to
--the FileStreamPhotoDB database.
ALTER database FileStreamPhotoDB
ADD FILEGROUP TodaysPhotoShoot
CONTAINS FILESTREAM
GO

--Add a file for storing database photos to FILEGROUP 
ALTER database FileStreamPhotoDB
ADD FILE
(
    NAME= 'PhotoShoot1',
    FILENAME = 'C:\Users\Administrator\Pictures\TodaysPhotoShoot.ndf'
)
TO FILEGROUP TodaysPhotoShoot
GO
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