On Windows, symbolic links can be used for database directories. This enables you to put a database directory at a different location (for example, on a different disk) by setting up a symbolic link to it. Use of database symlinks on Windows is similar to their use on Unix, although the procedure for setting up the link differs.
Suppose that you want to place the database directory for a
database named mydb at
D:\data\mydb. To do this, create a
symbolic link in the MySQL data directory that points to
D:\data\mydb. However, before creating
the symbolic link, make sure that the
D:\data\mydb directory exists by creating
it if necessary. If you already have a database directory
named mydb in the data directory, move it
to D:\data. Otherwise, the symbolic link
will be ineffective. To avoid problems, make sure that the
server is not running when you move the database directory.
The procedure for creating the database symbolic link depends on your version of Windows.
Windows Vista, Windows Server 2008, or newer have native symbolic link support, so you can create a symlink using the mklink command. This command requires administrative privileges.
Change location into the data directory:
C:\> cd \path\to\datadir
In the data directory, create a symlink named
mydb that points to the location of
the database directory:
C:\> mklink /d mydb D:\data\mydb
After this, all tables created in the database
mydb are created in
D:\data\mydb.
Alternatively, on any version of Windows supported by MySQL,
you can create a symbolic link to a MySQL database by creating
a .sym file in the data directory that
contains the path to the destination directory. The file
should be named
db_name.symdb_name is the database name.
Support for database symbolic links on Windows using
.sym files is enabled by default. If you
do not need .sym file symbolic links, you
can disable support for them by starting
mysqld with the
--skip-symbolic-links
option. To determine whether your system supports
.sym file symbolic links, check the value
of the have_symlink system
variable using this statement:
SHOW VARIABLES LIKE 'have_symlink';
To create a .sym file symlink, use this
procedure:
Change location into the data directory:
C:\> cd \path\to\datadir
In the data directory, create a text file named
mydb.sym that contains this path
name: D:\data\mydb\
The path name to the new database and tables should be
absolute. If you specify a relative path, the location
will be relative to the mydb.sym
file.
After this, all tables created in the database
mydb are created in
D:\data\mydb.
The following limitations apply to the use of
.sym files for database symbolic linking
on Windows. These limitations do not apply for symlinks
created using mklink.
The symbolic link is not used if a directory with the same name as the database exists in the MySQL data directory.
The --innodb_file_per_table
option cannot be used.
If you run mysqld as a service, you
cannot use a mapped drive to a remote server as the
destination of the symbolic link. As a workaround, you can
use the full path
(\\servername\path\).