isamchk − Description, check and repair of ISAM tables. Used without options all tables on the command will be checked for errors


isamchk [OPTIONS] tables[.ISM]


isamchk [−a|−−analyze] [−#|−−debug=...] [−−character−sets−dir=...] [−C|−−default−character−set=...] [−d|−−description] [−e|−−extend−check] [−f|−−force] [−?|−−help] [−i|−−information] [−k|−−keys−used=#] [−l|−−no−symlinks] [−q|−−quick] [−r|−−recover] [−o|−−safe−recover] [−O|−−set−variable var=option] [−s|−−silent] [−S|−−sort−index] [−R|−−sort−records=#] [−u|−−unpack] [−v|−−verbose] [−V|−−version] [−w|−−wait]



Analyze distribution of keys. Will make some joins in MySQL faster.


Output debug log. Often this is ’d:t:o ,filename‘


Directory where character sets are


Set the default character set


Prints some information about table.


Check the table VERY thoroughly. One need use this only in extreme cases as isamchk should normally find all errors even without this switch


Overwrite old temporary files. If one uses −f when checking tables (running isamchk without −r), isamchk will automatically restart with −r on any wrong table.


Display help and exit.


Print statistics information about the table


Used with ’−r’. Tell ISAM to update only the first # keys. This can be used to get faster inserts!


Do not follow symbolic links when repairing. Normally isamchk repairs the table a symlink points at.


Used with −r to get a faster repair. (The data file isn’t touched.) One can give a second ’−q’ to force isamchk to modify the original datafile.


Can fix almost anything except unique keys that aren’t unique.


Uses old recovery method; slower than ’−r’ but can handle a couple of cases that ’−r’ cannot handle.

−O| −−set−variable var=option

Change the value of a variable.


Only print errors. One can use two −s to make isamchk very silent


Sort index blocks. This speeds up ’read−next’ in applications


Sort records according to an index. This makes your data much more localized and may speed up things (It may be VERY slow to do a sort the first time!)


Unpack file packed with pack_isam.


Print more information. This can be used with −d and −e. Use many −v for more verbosity!


Print version and exit.


Wait if table is locked.


isamchk (1), isamlog (1), mysqlaccess (1), mysqladmin (1), mysqlbug (1), mysqld (1), mysqldump (1), mysqlshow (1), msql2mysql (1), perror (1), replace (1), safe_mysqld (1), which1 (1), zap (1),


Ver 1.0, distribution 3.23.29a Michael (Monty) Widenius (, TCX Datakonsult AB ( This software comes with no warranty. Manual page by L. (Kill-9) Pedersen (kill-9@kill−, Mercurmedia Data Model Architect / system developer (