Chapter 11 Windows Platform Restrictions

The following restrictions apply to use of MySQL on the Windows platform:

• Process memory

  On Windows 32-bit platforms, it is not possible by default to use more than 2GB of RAM within a single process, including MySQL. This is because the physical address limit on Windows 32-bit is 4GB and the default setting within Windows is to split the virtual address space between kernel (2GB) and user/applications (2GB).

  Some versions of Windows have a boot time setting to enable larger applications by reducing the kernel application. Alternatively, to use more than 2GB, use a 64-bit version of Windows.

• File system aliases

  When using MyISAM tables, you cannot use aliases within Windows link to the data files on another volume and then link back to the main MySQL datadir location.

  This facility is often used to move the data and index files to a RAID or other fast solution, while retaining the main .frm files in the default data directory configured with the datadir option.

• Limited number of ports

  Windows systems have about 4,000 ports available for client connections, and after a connection on a port closes, it takes two to four minutes before the port can be reused. In situations where clients connect to and disconnect from the server at a high rate, it is possible for all available ports to be used up before closed ports become available again. If this happens, the MySQL server appears to be unresponsive even though it is running. Ports may be used by other applications running on the machine as well, in which case the number of ports available to MySQL is lower.

  For more information about this problem, see https://support.microsoft.com/kb/196271.

• DATA DIRECTORY and INDEX DIRECTORY

  The DATA DIRECTORY clause of the CREATE TABLE statement is supported on Windows for InnoDB tables only, as described in Creating Tables Externally. For MyISAM and other storage engines, the DATA DIRECTORY and INDEX DIRECTORY clauses for CREATE TABLE are ignored on Windows and any other platforms with a nonfunctional realpath() call.

• DROP DATABASE

  You cannot drop a database that is in use by another session.

• Case-insensitive names

  File names are not case-sensitive on Windows, so MySQL database and table names are also not case-sensitive on Windows. The only restriction is that database and table names must be specified using the same case throughout a given statement. See Identifier Case Sensitivity.

• Directory and file names

  On Windows, MySQL Server supports only directory and file names that are compatible with the current ANSI code pages. For example, the following Japanese directory name does not work in the Western locale (code page 1252):

  datadir="C:/私たちのプロジェクトのデータ"

  The same limitation applies to directory and file names referred to in SQL statements, such as the data file path name in LOAD DATA.

• The \ path name separator character

  Path name components in Windows are separated by the \ character, which is also the escape character in MySQL. If you are using LOAD DATA or SELECT ... INTO OUTFILE, use Unix-style file names with / characters:

  mysql> LOAD DATA INFILE 'C:/tmp/skr.txt' INTO TABLE skr;
  mysql> SELECT * INTO OUTFILE 'C:/tmp/skr.txt' FROM skr;

  Alternatively, you must double the \ character:

  mysql> LOAD DATA INFILE 'C:\\tmp\\skr.txt' INTO TABLE skr;
  mysql> SELECT * INTO OUTFILE 'C:\\tmp\\skr.txt' FROM skr;

• Problems with pipes

  Pipes do not work reliably from the Windows command-line prompt. If the pipe includes the character ^Z / CHAR(24), Windows thinks that it has encountered end-of-file and aborts the program.

  This is mainly a problem when you try to apply a binary log as follows:

  C:\> mysqlbinlog binary_log_file | mysql --user=root

  If you have a problem applying the log and suspect that it is because of a ^Z / CHAR(24) character, you can use the following workaround:

  C:\> mysqlbinlog binary_log_file --result-file=/tmp/bin.sql
  C:\> mysql --user=root --execute "source /tmp/bin.sql"

  The latter command also can be used to reliably read any SQL file that may contain binary data.