Server System Variables The default mode value to use for the  WEEK()  function. See Section 12.7, “Date and Time Functions” . • delay_key_write Command-Line Format --delay-key-write[={OFF|ON|ALL}] System Variable delay_key_write Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Enumeration Default Value ON Valid Values ON OFF ALL This variable specifies how to use delayed key writes. It applies only to  MyISAM  tables. Delayed key writing causes key buffers not to be flushed between writes. See also Section 16.2.1, “MyISAM Startup Options” . This variable can have one of the following values to affect handling of the  DELAY_KEY_WRITE  table option that can be used in  CREATE TABLE  statements. Option Description OFF DELAY_KEY_WRITE  is ignored. ON MySQL honors any  DELAY_KEY_WRITE  option specified in  CREATE TABLE  statements. This is the default value. ALL All new opened tables are treated as if they were created with the  DELAY_KEY_WRITE  option enabled. Note If you set this variable to  ALL , you should not use  MyISAM  tables from within another program (such as another MySQL server or  myisamchk ) when the tables are in use. Doing so leads to index corruption. If  DELAY_KEY_WRITE  is enabled for a table, the key buffer is not flushed for the table on every index update, but only when the table is closed. This speeds up writes on keys a lot, but if you use this feature, you should add automatic checking of all  MyISAM  tables by starting the server with the  myisam_recover_options  system variable set (for example, 791 7 Maximum Value