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   myisamchk    ( 1 )

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MYISAMCHK REPAIR OPTIONS

myisamchk supports the following options for table repair operations (operations performed when an option such as --recover or --safe-recover is given):

• --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.

• --correct-checksum

Correct the checksum information for the table.

• --create-missing-keys

Create missing keys. This assumes that the data file is correct and that the number of rows stored in the index file is correct. Enables --quick.

• --data-file-length=len, -D len

The maximum length of the data file (when re-creating data file when it is '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. Do not use this option unless you are desperate.

For a description of the output format, see the section called 'MYISAMCHK TABLE INFORMATION'.

• --force, -f

Overwrite old intermediate files (files with names like tbl_name.TMD) instead of aborting. Add another --force to avoid 'myisam_sort_buffer_size is too small' errors. In this case we will attempt to do the repair with the given myisam_sort_buffer_size and dynamically allocate as many management buffers as needed.

• --keys-used=val, -k val

For myisamchk, the option value is a bit-value that indicates which indexes to update. Each binary bit of the option value corresponds to a table index, where the first index is bit 0. 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.

• --max-record-length=len

Skip rows larger than the given length if myisamchk cannot allocate memory to hold them.

• --parallel-recover, -p

Use the same technique as -r and -n, but create all the keys in parallel, using different threads. This is beta-quality code. Use at your own risk!

• --quick, -q

Achieve a faster repair by modifying only the index file, not the data file. You can specify this option twice to force myisamchk to modify the original data file in case of duplicate keys. NOTE: Tables where the data file is corrupted can't be fixed with this option.

• --recover, -r

Do a repair that can fix almost any problem except unique keys that are not unique (which is an extremely unlikely error with MyISAM tables). If you want to recover a table, this is the option to try first. You should try --safe-recover only if myisamchk reports that the table cannot be recovered using --recover. (In the unlikely case that --recover fails, the data file remains 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 --recover, but can handle a couple of very unlikely cases that --recover cannot. This recovery method also uses much less disk space than --recover. Normally, you should repair first using --recover, and then with --safe-recover only if --recover fails.

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

• --set-collation=name

Specify the collation to use for sorting table indexes. The character set name is implied by the first part of the collation name.

• --sort-recover, -n

Force myisamchk to use sorting to resolve the keys even if the temporary files would be very large.

• --tmpdir=path, -t path

The 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. 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 is the colon (':') on Unix and the semicolon (';') on Windows, NetWare, and OS/2.

• --unpack, -u

Unpack a table that was packed with myisampack.