Server System Variables The maximum size of the temporary file that MySQL is permitted to use while re-creating a  MyISAM index (during  REPAIR TABLE ,  ALTER TABLE , or  LOAD DATA ). If the file size would be larger than this value, the index is created using the key cache instead, which is slower. The value is given in bytes. If  MyISAM index files exceed this size and disk space is available, increasing the value may help performance. The space must be available in the file system containing the directory where the original index file is located. The maximum amount of memory to use for memory mapping compressed  MyISAM  files. If many compressed  MyISAM tables are used, the value can be decreased to reduce the likelihood of memory- swapping problems. 839 • myisam_recover_options • myisam_mmap_size Maximum Value (Other, 32-bit platforms) 2147483648 Command-Line Format --myisam-mmap-size=# System Variable myisam_mmap_size Scope Global Dynamic No SET_VAR  Hint Applies No Type Integer Default Value (64-bit platforms) 18446744073709551615 Default Value (32-bit platforms) 4294967295 Minimum Value 7 Maximum Value (64-bit platforms) 18446744073709551615 Maximum Value (32-bit platforms) 4294967295 Command-Line Format --myisam-recover-options[=list] System Variable myisam_recover_options Scope Global Dynamic No SET_VAR  Hint Applies No Type Enumeration Default Value OFF Valid Values OFF DEFAULT BACKUP FORCE