(mysql.info) myisamchk-memory

Info Catalog

(mysql.info) myisamchk-other-options

(mysql.info) myisamchk

 
 8.2.5 `myisamchk' Memory Usage
 ------------------------------
 
 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 32MB
 RAM, you could use options such as these (in addition to any other
 options you might specify):
 
      shell> myisamchk --sort_buffer_size=16M --key_buffer_size=16M \
                 --read_buffer_size=1M --write_buffer_size=1M ...
 
 Using -sort_buffer_size=16M should probably be enough for most cases.
 
 Be aware that `myisamchk' uses temporary files in `TMPDIR'. If `TMPDIR'
 points to a memory filesystem, you may easily get out of memory errors.
 If this happens, run `myisamchk' with the -tmpdir=PATH option to
 specify some directory located on a filesystem that has more space.
 
 When repairing, `myisamchk' also needs a lot of disk space:
 
    * Double 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 is needed on
      the same filesystem as the original data file! (The copy is created
      in the same directory as the original.)
 
    * 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 is needed on the same
      filesystem as the original index file!
 
    * When using -recover or -sort-recover (but not when using
      -safe-recover), you need space for a sort buffer. 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'. This space is allocated in the
      temporary directory (specified by `TMPDIR' or -tmpdir=PATH).
 
 If you have a problem with disk space during repair, you can try
 -safe-recover instead of -recover.
 

Info Catalog

(mysql.info) myisamchk-other-options

(mysql.info) myisamchk