Additional Resources • myisamchk  marks tables as checked if you run it with the  --update-state  option.  myisamchk -- fast  checks only those tables that don’t have this mark. • myisamchk --analyze  stores statistics for portions of keys, as well as for entire keys. • myisampack  can pack  BLOB  and  VARCHAR  columns. •Support for a true  VARCHAR  type; a  VARCHAR  column starts with a length stored in one or two bytes. •Tables with  VARCHAR  columns may have fixed or dynamic row length. •The sum of the lengths of the  VARCHAR  and  CHAR  columns in a table may be up to 64KB. •Arbitrary length  UNIQUE  constraints. MyISAM  also supports the following features: Additional Resources 16.2.1 MyISAM Startup Options •A forum dedicated to the  MyISAM  storage engine is available at https://forums.mysql.com/list.php?21. The following options to  mysqld  can be used to change the behavior of  MyISAM  tables. For additional information, see Section 5.1.7, “Server Command Options” . Table 16.3 MyISAM Option and Variable Reference Name Cmd-Line Option File System Var Status Var Var Scope Dynamic bulk_insert_buffer_size Yes Yes Yes Both Yes concurrent_insert Yes Yes Yes Global Yes delay_key_write Yes Yes Yes Global Yes have_rtree_keys Yes Global No key_buffer_size Yes Yes Yes Global Yes log-isam Yes Yes myisam- block-size Yes Yes myisam_data_pointer_size Yes Yes Yes Global Yes myisam_max_sort_file_size Yes Yes Yes Global Yes myisam_mmap_size Yes Yes Yes Global No myisam_recover_options Yes Yes Yes Global No myisam_repair_threads Yes Yes Yes Both Yes myisam_sort_buffer_size Yes Yes Yes Both Yes myisam_stats_method Yes Yes Yes Both Yes myisam_use_mmap Yes Yes Yes Global Yes tmp_table_size Yes Yes Yes Both Yes The following system variables affect the behavior of  MyISAM  tables. For additional information, see Section 5.1.8, “Server System Variables” . • bulk_insert_buffer_size 3404