MySQL Reference Manual :: 5.8.3.4 Repair Options for myisamchk

--backup, -B

Make a backup of the .MYD file as file_name-time.BAK

--character-sets-dir=path

The directory where character sets are installed. See Section 5.9.1, “The Character Set Used for Data and Sorting”.

--correct-checksum

Correct the checksum information for the table.

--data-file-length=#, -D #

Maximum length of the data file (when re-creating data file when it's ``full'').

--extend-check, -e

Do a repair that tries to recover every possible row from the data file. Normally this also finds a lot of garbage rows. Don't use this option unless you are totally desperate.

--force, -f

Overwrite old temporary files (files with names like tbl_name.TMD) instead of aborting.

--keys-used=#, -k #

For myisamchk, the option value indicates which indexes to update. Each binary bit of the option value corresponds to a table index, where the first index is bit 0. For isamchk, the option value indicates that only the first # of the table indexes should be updated. In either case, an option value of 0 disables updates to all indexes, which can be used to get faster inserts. Deactivated indexes can be reactivated by using myisamchk -r or (isamchk -r).

--no-symlinks, -l

Do not follow symbolic links. Normally myisamchk repairs the table that a symlink points to. This option doesn't exist as of MySQL 4.0, because versions from 4.0 on do not remove symlinks during repair operations.

--parallel-recover, -p

Uses the same technique as -r and -n, but creates all the keys in parallel, using different threads. This option was added in MySQL 4.0.2. This is alpha code. Use at your own risk!

--quick, -q

Achieve a faster repair by not modifying the data file. You can specify this option twice to force myisamchk to modify the original data file in case of duplicate keys.

--recover, -r

Do a repair that can fix almost any problem except unique keys that aren't unique (which is an extremely unlikely error with ISAM/MyISAM tables). If you want to recover a table, this is the option to try first. You should try -o only if myisamchk reports that the table can't be recovered by -r. (In the unlikely case that -r fails, the data file is still intact.)

If you have lots of memory, you should increase the value of sort_buffer_size.

--safe-recover, -o

Do a repair using an old recovery method that reads through all rows in order and updates all index trees based on the rows found. This is an order of magnitude slower than -r, but can handle a couple of very unlikely cases that -r cannot. This recovery method also uses much less disk space than -r. Normally, you should repair first with -r, and then with -o only if -r fails.

If you have lots of memory, you should increase the value of key_buffer_size.

--set-character-set=name

Change the character set used by the table indexes. This option was replaced by --set-collation in MySQL 4.1.1/5.0.3.

--set-collation=name

Change the collation used to sort table indexes. The character set name is implied by the first part of the collation name. This option was added in MySQL 4.1.11/5.0.3.

--sort-recover, -n

Force myisamchk to use sorting to resolve the keys even if the temporary files should be very big.

--tmpdir=path, -t path

Path of the directory to be used for storing temporary files. If this is not set, myisamchk uses the value of the TMPDIR environment variable. Starting from MySQL 4.1, tmpdir can be set to a list of directory paths that are used successively in round-robin fashion for creating temporary files. The separator character between directory names should be colon (':') on Unix and semicolon (';') on Windows, NetWare, and OS/2.

--unpack, -u

Unpack a table that was packed with myisampack.