myisampack — Generate Compressed, Read-Only MyISAM Tables Perform an update operation. Verbose mode. Print more output about what the program does. This option can be given multiple times to produce more and more output. Display version information. Specify the write file. The  myisampack  utility compresses  MyISAM  tables.  myisampack  works by compressing each column in the table separately. Usually,  myisampack  packs the data file 40% to 70%. When the table is used later, the server reads into memory the information needed to decompress columns. This results in much better performance when accessing individual rows, because you only have to uncompress exactly one row. MySQL uses  mmap()  when possible to perform memory mapping on compressed tables. If  mmap()  does not work, MySQL falls back to normal read/write file operations. Please note the following: Invoke  myisampack  like this: Each file name argument should be the name of an index ( .MYI ) file. If you are not in the database directory, you should specify the path name to the file. It is permissible to omit the  .MYI  extension. After you compress a table with  myisampack , use  myisamchk -rq  to rebuild its indexes. Section 4.6.4, “myisamchk — MyISAM Table-Maintenance Utility” . myisampack  supports the following options. It also reads option files and supports the options for processing them described at Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling” . Display a help message and exit. 580 • --backup ,  -b • --help ,  -? • myisampack  does not support partitioned tables. •After packing a table, it becomes read only. This is generally intended (such as when accessing packed tables on a CD). •If the  mysqld  server was invoked with external locking disabled, it is not a good idea to invoke myisampack  if the table might be updated by the server during the packing process. It is safest to compress tables with the server stopped. • -V • -w  write_file • -v 4.6.6 myisampack — Generate Compressed, Read-Only MyISAM Tables myisampack [ options ]  file_name  ...