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MYISAMCHK(1)		     MySQL Database System		  MYISAMCHK(1)

       myisamchk - MyISAM table-maintenance utility

       myisamchk [options] tbl_name ...

       The myisamchk utility gets information about your database tables or
       checks, repairs, or optimizes them.  myisamchk works with MyISAM tables
       (tables that have .MYD and .MYI files for storing data and indexes).

       You can also use the CHECK TABLE and REPAIR TABLE statements to check
       and repair MyISAM tables. See Section, "CHECK TABLE Syntax",
       and Section, "REPAIR TABLE Syntax".

       The use of myisamchk with partitioned tables is not supported.

	   It is best to make a backup of a table before performing a table
	   repair operation; under some circumstances the operation might
	   cause data loss. Possible causes include but are not limited to
	   file system errors.

       Invoke myisamchk like this:

	   shell> myisamchk [options] tbl_name ...

       The options specify what you want myisamchk to do. They are described
       in the following sections. You can also get a list of options by
       invoking myisamchk --help.

       With no options, myisamchk simply checks your table as the default
       operation. To get more information or to tell myisamchk to take
       corrective action, specify options as described in the following

       tbl_name is the database table you want to check or repair. If you run
       myisamchk somewhere other than in the database directory, you must
       specify the path to the database directory, because myisamchk has no
       idea where the database is located. In fact, myisamchk does not
       actually care whether the files you are working on are located in a
       database directory. You can copy the files that correspond to a
       database table into some other location and perform recovery operations
       on them there.

       You can name several tables on the myisamchk command line if you wish.
       You can also specify a table by naming its index file (the file with
       the .MYI suffix). This enables you to specify all tables in a directory
       by using the pattern *.MYI. For example, if you are in a database
       directory, you can check all the MyISAM tables in that directory like

	   shell> myisamchk *.MYI

       If you are not in the database directory, you can check all the tables
       there by specifying the path to the directory:

	   shell> myisamchk /path/to/database_dir/*.MYI

       You can even check all tables in all databases by specifying a wildcard
       with the path to the MySQL data directory:

	   shell> myisamchk /path/to/datadir/*/*.MYI

       The recommended way to quickly check all MyISAM tables is:

	   shell> myisamchk --silent --fast /path/to/datadir/*/*.MYI

       If you want to check all MyISAM tables and repair any that are
       corrupted, you can use the following command:

	   shell> myisamchk --silent --force --fast --update-state \
		     --key_buffer_size=64M --myisam_sort_buffer_size=64M \
		     --read_buffer_size=1M --write_buffer_size=1M \

       This command assumes that you have more than 64MB free. For more
       information about memory allocation with myisamchk, see the section

       For additional information about using myisamchk, see Section 7.6,
       "MyISAM Table Maintenance and Crash Recovery".

	   You must ensure that no other program is using the tables while you
	   are running myisamchk. The most effective means of doing so is to
	   shut down the MySQL server while running myisamchk, or to lock all
	   tables that myisamchk is being used on.

	   Otherwise, when you run myisamchk, it may display the following
	   error message:

	       warning: clients are using or haven't closed the table properly

	   This means that you are trying to check a table that has been
	   updated by another program (such as the mysqld server) that hasn't
	   yet closed the file or that has died without closing the file
	   properly, which can sometimes lead to the corruption of one or more
	   MyISAM tables.

	   If mysqld is running, you must force it to flush any table
	   modifications that are still buffered in memory by using FLUSH
	   TABLES. You should then ensure that no one is using the tables
	   while you are running myisamchk

	   However, the easiest way to avoid this problem is to use CHECK
	   TABLE instead of myisamchk to check tables. See Section,
	   "CHECK TABLE Syntax".

       myisamchk supports the following options, which can be specified on the
       command line or in the [myisamchk] group of an option file. For
       information about option files used by MySQL programs, see
       Section 4.2.6, "Using Option Files".

       The options described in this section can be used for any type of table
       maintenance operation performed by myisamchk. The sections following
       this one describe options that pertain only to specific operations,
       such as table checking or repairing.

       o   --help, -?

	   Display a help message and exit. Options are grouped by type of

       o   --HELP, -H

	   Display a help message and exit. Options are presented in a single

       o   --debug=debug_options, -# debug_options

	   Write a debugging log. A typical debug_options string is
	   d:t:o,file_name. The default is d:t:o,/tmp/myisamchk.trace.

       o   --defaults-extra-file=file_name

	   Read this option file after the global option file but (on Unix)
	   before the user option file. If the file does not exist or is
	   otherwise inaccessible, an error occurs.  file_name is interpreted
	   relative to the current directory if given as a relative path name.

       o   --defaults-file=file_name

	   Use only the given option file. If the file does not exist or is
	   otherwise inaccessible, an error occurs.  file_name is interpreted
	   relative to the current directory if given as a relative path name.

       o   --defaults-group-suffix=str

	   Read not only the usual option groups, but also groups with the
	   usual names and a suffix of str. For example, myisamchk normally
	   reads the [myisamchk] group. If the --defaults-group-suffix=_other
	   option is given, myisamchk also reads the [myisamchk_other] group.

       o   --no-defaults

	   Do not read any option files. If program startup fails due to
	   reading unknown options from an option file, --no-defaults can be
	   used to prevent them from being read.

       o   --print-defaults

	   Print the program name and all options that it gets from option

       o   --silent, -s

	   Silent mode. Write output only when errors occur. You can use -s
	   twice (-ss) to make myisamchk very silent.

       o   --verbose, -v

	   Verbose mode. Print more information about what the program does.
	   This can be used with -d and -e. Use -v multiple times (-vv, -vvv)
	   for even more output.

       o   --version, -V

	   Display version information and exit.

       o   --wait, -w

	   Instead of terminating with an error if the table is locked, wait
	   until the table is unlocked before continuing. If you are running
	   mysqld with external locking disabled, the table can be locked only
	   by another myisamchk command.

       You can also set the following variables by using --var_name=value

       |Variable	       | Default Value	   |
       |decode_bits	       | 9		   |
       |ft_max_word_len	       | version-dependent |
       |ft_min_word_len	       | 4		   |
       |ft_stopword_file       | built-in list	   |
       |key_buffer_size	       | 523264		   |
       |myisam_block_size      | 1024		   |
       |myisam_sort_key_blocks | 16		   |
       |read_buffer_size       | 262136		   |
       |sort_buffer_size       | 2097144	   |
       |sort_key_blocks	       | 16		   |
       |stats_method	       | nulls_unequal	   |
       |write_buffer_size      | 262136		   |

       The possible myisamchk variables and their default values can be
       examined with myisamchk --help:

       sort_buffer_size is used when the keys are repaired by sorting keys,
       which is the normal case when you use --recover. As of MySQL 5.5.29,
       myisam_sort_buffer_size is available as an alternative name to
       sort_buffer_size.  myisam_sort_buffer_size is preferable to
       sort_buffer_size because its name corresponds to the
       myisam_sort_buffer_size server system variable that has a similar
       meaning.	 sort_buffer_size should be considered deprecated.

       key_buffer_size is used when you are checking the table with
       --extend-check or when the keys are repaired by inserting keys row by
       row into the table (like when doing normal inserts). Repairing through
       the key buffer is used in the following cases:

       o   You use --safe-recover.

       o   The temporary files needed to sort the keys would be more than
	   twice as big as when creating the key file directly. This is often
	   the case when you have large key values for CHAR, VARCHAR, or TEXT
	   columns, because the sort operation needs to store the complete key
	   values as it proceeds. If you have lots of temporary space and you
	   can force myisamchk to repair by sorting, you can use the
	   --sort-recover option.

       Repairing through the key buffer takes much less disk space than using
       sorting, but is also much slower.

       If you want a faster repair, set the key_buffer_size and
       myisam_sort_buffer_size variables to about 25% of your available
       memory. You can set both variables to large values, because only one of
       them is used at a time.

       myisam_block_size is the size used for index blocks.

       stats_method influences how NULL values are treated for index
       statistics collection when the --analyze option is given. It acts like
       the myisam_stats_method system variable. For more information, see the
       description of myisam_stats_method in Section 5.1.7, "Server System
       Variables", and Section 8.3.7, "InnoDB and MyISAM Index Statistics

       ft_min_word_len and ft_max_word_len indicate the minimum and maximum
       word length for FULLTEXT indexes.  ft_stopword_file names the stopword
       file. These need to be set under the following circumstances.

       If you use myisamchk to perform an operation that modifies table
       indexes (such as repair or analyze), the FULLTEXT indexes are rebuilt
       using the default full-text parameter values for minimum and maximum
       word length and the stopword file unless you specify otherwise. This
       can result in queries failing.

       The problem occurs because these parameters are known only by the
       server. They are not stored in MyISAM index files. To avoid the problem
       if you have modified the minimum or maximum word length or the stopword
       file in the server, specify the same ft_min_word_len, ft_max_word_len,
       and ft_stopword_file values to myisamchk that you use for mysqld. For
       example, if you have set the minimum word length to 3, you can repair a
       table with myisamchk like this:

	   shell> myisamchk --recover --ft_min_word_len=3 tbl_name.MYI

       To ensure that myisamchk and the server use the same values for
       full-text parameters, you can place each one in both the [mysqld] and
       [myisamchk] sections of an option file:


       An alternative to using myisamchk is to use the REPAIR TABLE, ANALYZE
       TABLE, OPTIMIZE TABLE, or ALTER TABLE. These statements are performed
       by the server, which knows the proper full-text parameter values to

       myisamchk supports the following options for table checking operations:

       o   --check, -c

	   Check the table for errors. This is the default operation if you
	   specify no option that selects an operation type explicitly.

       o   --check-only-changed, -C

	   Check only tables that have changed since the last check.

       o   --extend-check, -e

	   Check the table very thoroughly. This is quite slow if the table
	   has many indexes. This option should only be used in extreme cases.
	   Normally, myisamchk or myisamchk --medium-check should be able to
	   determine whether there are any errors in the table.

	   If you are using --extend-check and have plenty of memory, setting
	   the key_buffer_size variable to a large value helps the repair
	   operation run faster.

	   See also the description of this option under table repair options.

	   For a description of the output format, see the section called

       o   --fast, -F

	   Check only tables that haven't been closed properly.

       o   --force, -f

	   Do a repair operation automatically if myisamchk finds any errors
	   in the table. The repair type is the same as that specified with
	   the --recover or -r option.

       o   --information, -i

	   Print informational statistics about the table that is checked.

       o   --medium-check, -m

	   Do a check that is faster than an --extend-check operation. This
	   finds only 99.99% of all errors, which should be good enough in
	   most cases.

       o   --read-only, -T

	   Do not mark the table as checked. This is useful if you use
	   myisamchk to check a table that is in use by some other application
	   that does not use locking, such as mysqld when run with external
	   locking disabled.

       o   --update-state, -U

	   Store information in the .MYI file to indicate when the table was
	   checked and whether the table crashed. This should be used to get
	   full benefit of the --check-only-changed option, but you shouldn't
	   use this option if the mysqld server is using the table and you are
	   running it with external locking disabled.

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

       o   --backup, -B

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

       o   --character-sets-dir=dir_name

	   The directory where character sets are installed. See
	   Section 10.14, "Character Set Configuration".

       o   --correct-checksum

	   Correct the checksum information for the table.

       o   --data-file-length=len, -D len

	   The maximum length of the data file (when re-creating data file
	   when it is "full").

       o   --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.

	   See also the description of this option under table checking

	   For a description of the output format, see the section called

       o   --force, -f

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

       o   --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.

       o   --no-symlinks, -l

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

       o   --max-record-length=len

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

       o   --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!

       o   --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.

       o   --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

       o   --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

       o   --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

       o   --sort-recover, -n

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

       o   --tmpdir=dir_name, -t dir_name

	   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.

       o   --unpack, -u

	   Unpack a table that was packed with myisampack.

       myisamchk supports the following options for actions other than table
       checks and repairs:

       o   --analyze, -a

	   Analyze the distribution of key values. This improves join
	   performance by enabling the join optimizer to better choose the
	   order in which to join the tables and which indexes it should use.
	   To obtain information about the key distribution, use a myisamchk
	   --description --verbose tbl_name command or the SHOW INDEX FROM
	   tbl_name statement.

       o   --block-search=offset, -b offset

	   Find the record that a block at the given offset belongs to.

       o   --description, -d

	   Print some descriptive information about the table. Specifying the
	   --verbose option once or twice produces additional information. See

       o   --set-auto-increment[=value], -A[value]

	   Force AUTO_INCREMENT numbering for new records to start at the
	   given value (or higher, if there are existing records with
	   AUTO_INCREMENT values this large). If value is not specified,
	   AUTO_INCREMENT numbers for new records begin with the largest value
	   currently in the table, plus one.

       o   --sort-index, -S

	   Sort the index tree blocks in high-low order. This optimizes seeks
	   and makes table scans that use indexes faster.

       o   --sort-records=N, -R N

	   Sort records according to a particular index. This makes your data
	   much more localized and may speed up range-based SELECT and ORDER
	   BY operations that use this index. (The first time you use this
	   option to sort a table, it may be very slow.) To determine a
	   table's index numbers, use SHOW INDEX, which displays a table's
	   indexes in the same order that myisamchk sees them. Indexes are
	   numbered beginning with 1.

	   If keys are not packed (PACK_KEYS=0), they have the same length, so
	   when myisamchk sorts and moves records, it just overwrites record
	   offsets in the index. If keys are packed (PACK_KEYS=1), myisamchk
	   must unpack key blocks first, then re-create indexes and pack the
	   key blocks again. (In this case, re-creating indexes is faster than
	   updating offsets for each index.)

       To obtain a description of a MyISAM table or statistics about it, use
       the commands shown here. The output from these commands is explained
       later in this section.

       o   myisamchk -d tbl_name

	   Runs myisamchk in "describe mode" to produce a description of your
	   table. If you start the MySQL server with external locking
	   disabled, myisamchk may report an error for a table that is updated
	   while it runs. However, because myisamchk does not change the table
	   in describe mode, there is no risk of destroying data.

       o   myisamchk -dv tbl_name

	   Adding -v runs myisamchk in verbose mode so that it produces more
	   information about the table. Adding -v a second time produces even
	   more information.

       o   myisamchk -eis tbl_name

	   Shows only the most important information from a table. This
	   operation is slow because it must read the entire table.

       o   myisamchk -eiv tbl_name

	   This is like -eis, but tells you what is being done.

       The tbl_name argument can be either the name of a MyISAM table or the
       name of its index file, as described in myisamchk(1). Multiple tbl_name
       arguments can be given.

       Suppose that a table named person has the following structure. (The
       MAX_ROWS table option is included so that in the example output from
       myisamchk shown later, some values are smaller and fit the output
       format more easily.)

	   CREATE TABLE person
	     last_name	VARCHAR(20) NOT NULL,
	     first_name VARCHAR(20) NOT NULL,
	     birth	DATE,
	     death	DATE,
	     PRIMARY KEY (id),
	     INDEX (last_name, first_name),
	     INDEX (birth)
	   ) MAX_ROWS = 1000000 ENGINE=MYISAM;

       Suppose also that the table has these data and index file sizes:

	   -rw-rw----  1 mysql	mysql  9347072 Aug 19 11:47 person.MYD
	   -rw-rw----  1 mysql	mysql  6066176 Aug 19 11:47 person.MYI

       Example of myisamchk -dvv output:

	   MyISAM file:		person
	   Record format:	Packed
	   Character set:	latin1_swedish_ci (8)
	   File-version:	1
	   Creation time:	2009-08-19 16:47:41
	   Recover time:	2009-08-19 16:47:56
	   Status:		checked,analyzed,optimized keys
	   Auto increment key:		    1  Last value:		  306688
	   Data records:	       306688  Deleted blocks:		       0
	   Datafile parts:	       306688  Deleted data:		       0
	   Datafile pointer (bytes):	    4  Keyfile pointer (bytes):	       3
	   Datafile length:	      9347072  Keyfile length:		 6066176
	   Max datafile length:	   4294967294  Max keyfile length:   17179868159
	   Recordlength:		   54
	   table description:
	   Key Start Len Index	 Type		      Rec/key	      Root  Blocksize
	   1   2     4	 unique	 long			    1	     99328	 1024
	   2   6     20	 multip. varchar prefix		  512	   3563520	 1024
	       27    20		 varchar		  512
	   3   48    3	 multip. uint24 NULL	       306688	   6065152	 1024
	   Field Start Length Nullpos Nullbit Type
	   1	 1     1
	   2	 2     4		      no zeros
	   3	 6     21		      varchar
	   4	 27    21		      varchar
	   5	 48    3      1	      1	      no zeros
	   6	 51    3      1	      2	      no zeros

       Explanations for the types of information myisamchk produces are given
       here.  "Keyfile" refers to the index file.  "Record" and "row" are
       synonymous, as are "field" and "column."

       The initial part of the table description contains these values:

       o   MyISAM file

	   Name of the MyISAM (index) file.

       o   Record format

	   The format used to store table rows. The preceding examples use
	   Fixed length. Other possible values are Compressed and Packed.
	   (Packed corresponds to what SHOW TABLE STATUS reports as Dynamic.)

       o   Chararacter set

	   The table default character set.

       o   File-version

	   Version of MyISAM format. Always 1.

       o   Creation time

	   When the data file was created.

       o   Recover time

	   When the index/data file was last reconstructed.

       o   Status

	   Table status flags. Possible values are crashed, open, changed,
	   analyzed, optimized keys, and sorted index pages.

       o   Auto increment key, Last value

	   The key number associated the table's AUTO_INCREMENT column, and
	   the most recently generated value for this column. These fields do
	   not appear if there is no such column.

       o   Data records

	   The number of rows in the table.

       o   Deleted blocks

	   How many deleted blocks still have reserved space. You can optimize
	   your table to minimize this space. See Section 7.6.4, "MyISAM Table

       o   Datafile parts

	   For dynamic-row format, this indicates how many data blocks there
	   are. For an optimized table without fragmented rows, this is the
	   same as Data records.

       o   Deleted data

	   How many bytes of unreclaimed deleted data there are. You can
	   optimize your table to minimize this space. See Section 7.6.4,
	   "MyISAM Table Optimization".

       o   Datafile pointer

	   The size of the data file pointer, in bytes. It is usually 2, 3, 4,
	   or 5 bytes. Most tables manage with 2 bytes, but this cannot be
	   controlled from MySQL yet. For fixed tables, this is a row address.
	   For dynamic tables, this is a byte address.

       o   Keyfile pointer

	   The size of the index file pointer, in bytes. It is usually 1, 2,
	   or 3 bytes. Most tables manage with 2 bytes, but this is calculated
	   automatically by MySQL. It is always a block address.

       o   Max datafile length

	   How long the table data file can become, in bytes.

       o   Max keyfile length

	   How long the table index file can become, in bytes.

       o   Recordlength

	   How much space each row takes, in bytes.

       The table description part of the output includes a list of all keys in
       the table. For each key, myisamchk displays some low-level information:

       o   Key

	   This key's number. This value is shown only for the first column of
	   the key. If this value is missing, the line corresponds to the
	   second or later column of a multiple-column key. For the table
	   shown in the example, there are two table description lines for the
	   second index. This indicates that it is a multiple-part index with
	   two parts.

       o   Start

	   Where in the row this portion of the index starts.

       o   Len

	   How long this portion of the index is. For packed numbers, this
	   should always be the full length of the column. For strings, it may
	   be shorter than the full length of the indexed column, because you
	   can index a prefix of a string column. The total length of a
	   multiple-part key is the sum of the Len values for all key parts.

       o   Index

	   Whether a key value can exist multiple times in the index. Possible
	   values are unique or multip.	 (multiple).

       o   Type

	   What data type this portion of the index has. This is a MyISAM data
	   type with the possible values packed, stripped, or empty.

       o   Root

	   Address of the root index block.

       o   Blocksize

	   The size of each index block. By default this is 1024, but the
	   value may be changed at compile time when MySQL is built from

       o   Rec/key

	   This is a statistical value used by the optimizer. It tells how
	   many rows there are per value for this index. A unique index always
	   has a value of 1. This may be updated after a table is loaded (or
	   greatly changed) with myisamchk -a. If this is not updated at all,
	   a default value of 30 is given.

       The last part of the output provides information about each column:

       o   Field

	   The column number.

       o   Start

	   The byte position of the column within table rows.

       o   Length

	   The length of the column in bytes.

       o   Nullpos, Nullbit

	   For columns that can be NULL, MyISAM stores NULL values as a flag
	   in a byte. Depending on how many nullable columns there are, there
	   can be one or more bytes used for this purpose. The Nullpos and
	   Nullbit values, if nonempty, indicate which byte and bit contains
	   that flag indicating whether the column is NULL.

	   The position and number of bytes used to store NULL flags is shown
	   in the line for field 1. This is why there are six Field lines for
	   the person table even though it has only five columns.

       o   Type

	   The data type. The value may contain any of the following

	   o   constant

	       All rows have the same value.

	   o   no endspace

	       Do not store endspace.

	   o   no endspace, not_always

	       Do not store endspace and do not do endspace compression for
	       all values.

	   o   no endspace, no empty

	       Do not store endspace. Do not store empty values.

	   o   table-lookup

	       The column was converted to an ENUM.

	   o   zerofill(N)

	       The most significant N bytes in the value are always 0 and are
	       not stored.

	   o   no zeros

	       Do not store zeros.

	   o   always zero

	       Zero values are stored using one bit.

       o   Huff tree

	   The number of the Huffman tree associated with the column.

       o   Bits

	   The number of bits used in the Huffman tree.

       The Huff tree and Bits fields are displayed if the table has been
       compressed with myisampack. See myisampack(1), for an example of this

       Example of myisamchk -eiv output:

	   Checking MyISAM file: person
	   Data records:  306688   Deleted blocks:	 0
	   - check file-size
	   - check record delete-chain
	   No recordlinks
	   - check key delete-chain
	   block_size 1024:
	   - check index reference
	   - check data record references index: 1
	   Key:	 1:  Keyblocks used:  98%  Packed:    0%  Max levels:  3
	   - check data record references index: 2
	   Key:	 2:  Keyblocks used:  99%  Packed:   97%  Max levels:  3
	   - check data record references index: 3
	   Key:	 3:  Keyblocks used:  98%  Packed:  -14%  Max levels:  3
	   Total:    Keyblocks used:  98%  Packed:   89%
	   - check records and index references
	   Records:	       306688  M.recordlength:	     25	 Packed:	    83%
	   Recordspace used:	   97% Empty space:	      2% Blocks/Record:	  1.00
	   Record blocks:      306688  Delete blocks:	      0
	   Record data:	      7934464  Deleted data:	      0
	   Lost space:	       256512  Linkdata:	1156096
	   User time 43.08, System time 1.68
	   Maximum resident set size 0, Integral resident set size 0
	   Non-physical pagefaults 0, Physical pagefaults 0, Swaps 0
	   Blocks in 0 out 7, Messages in 0 out 0, Signals 0
	   Voluntary context switches 0, Involuntary context switches 0
	   Maximum memory usage: 1046926 bytes (1023k)

       myisamchk -eiv output includes the following information:

       o   Data records

	   The number of rows in the table.

       o   Deleted blocks

	   How many deleted blocks still have reserved space. You can optimize
	   your table to minimize this space. See Section 7.6.4, "MyISAM Table

       o   Key

	   The key number.

       o   Keyblocks used

	   What percentage of the keyblocks are used. When a table has just
	   been reorganized with myisamchk, the values are very high (very
	   near theoretical maximum).

       o   Packed

	   MySQL tries to pack key values that have a common suffix. This can
	   only be used for indexes on CHAR and VARCHAR columns. For long
	   indexed strings that have similar leftmost parts, this can
	   significantly reduce the space used. In the preceding example, the
	   second key is 40 bytes long and a 97% reduction in space is

       o   Max levels

	   How deep the B-tree for this key is. Large tables with long key
	   values get high values.

       o   Records

	   How many rows are in the table.

       o   M.recordlength

	   The average row length. This is the exact row length for tables
	   with fixed-length rows, because all rows have the same length.

       o   Packed

	   MySQL strips spaces from the end of strings. The Packed value
	   indicates the percentage of savings achieved by doing this.

       o   Recordspace used

	   What percentage of the data file is used.

       o   Empty space

	   What percentage of the data file is unused.

       o   Blocks/Record

	   Average number of blocks per row (that is, how many links a
	   fragmented row is composed of). This is always 1.0 for fixed-format
	   tables. This value should stay as close to 1.0 as possible. If it
	   gets too large, you can reorganize the table. See Section 7.6.4,
	   "MyISAM Table Optimization".

       o   Recordblocks

	   How many blocks (links) are used. For fixed-format tables, this is
	   the same as the number of rows.

       o   Deleteblocks

	   How many blocks (links) are deleted.

       o   Recorddata

	   How many bytes in the data file are used.

       o   Deleted data

	   How many bytes in the data file are deleted (unused).

       o   Lost space

	   If a row is updated to a shorter length, some space is lost. This
	   is the sum of all such losses, in bytes.

       o   Linkdata

	   When the dynamic table format is used, row fragments are linked
	   with pointers (4 to 7 bytes each).  Linkdata is the sum of the
	   amount of storage used by all such pointers.

       Memory allocation is important when you run myisamchk.  myisamchk uses
       no more memory than its memory-related variables are set to. If you are
       going to use myisamchk on very large tables, you should first decide
       how much memory you want it to use. The default is to use only about
       3MB to perform repairs. By using larger values, you can get myisamchk
       to operate faster. For example, if you have more than 512MB RAM
       available, you could use options such as these (in addition to any
       other options you might specify):

	   shell> myisamchk --myisam_sort_buffer_size=256M \
		      --key_buffer_size=512M \
		      --read_buffer_size=64M \
		      --write_buffer_size=64M ...

       Using --myisam_sort_buffer_size=16M is probably enough for most cases.

       Be aware that myisamchk uses temporary files in TMPDIR. If TMPDIR
       points to a memory file system, out of memory errors can easily occur.
       If this happens, run myisamchk with the --tmpdir=dir_name option to
       specify a directory located on a file system that has more space.

       When performing repair operations, myisamchk also needs a lot of disk

       o   Twice the size of the data file (the original file and a copy).
	   This space is not needed if you do a repair with --quick; in this
	   case, only the index file is re-created.  This space must be
	   available on the same file system as the original data file, as the
	   copy is created in the same directory as the original.

       o   Space for the new index file that replaces the old one. The old
	   index file is truncated at the start of the repair operation, so
	   you usually ignore this space. This space must be available on the
	   same file system as the original data file.

       o   When using --recover or --sort-recover (but not when using
	   --safe-recover), you need space on disk for sorting. This space is
	   allocated in the temporary directory (specified by TMPDIR or
	   --tmpdir=dir_name). The following formula yields the amount of
	   space required:

	       (largest_key + row_pointer_length) * number_of_rows * 2

	   You can check the length of the keys and the row_pointer_length
	   with myisamchk -dv tbl_name (see the section called "OBTAINING
	   TABLE INFORMATION WITH MYISAMCHK"). The row_pointer_length and
	   number_of_rows values are the Datafile pointer and Data records
	   values in the table description. To determine the largest_key
	   value, check the Key lines in the table description. The Len column
	   indicates the number of bytes for each key part. For a
	   multiple-column index, the key size is the sum of the Len values
	   for all key parts.

       If you have a problem with disk space during repair, you can try
       --safe-recover instead of --recover.

       Copyright (C) 1997, 2018, Oracle and/or its affiliates. All rights

       This documentation is free software; you can redistribute it and/or
       modify it only under the terms of the GNU General Public License as
       published by the Free Software Foundation; version 2 of the License.

       This documentation is distributed in the hope that it will be useful,
       but WITHOUT ANY WARRANTY; without even the implied warranty of
       General Public License for more details.

       You should have received a copy of the GNU General Public License along
       with the program; if not, write to the Free Software Foundation, Inc.,
       51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see

       For more information, please refer to the MySQL Reference Manual, which
       may already be installed locally and which is also available online at

       Oracle Corporation (http://dev.mysql.com/).

MySQL 5.5			  08/28/2018			  MYISAMCHK(1)