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    1. General Information
    2. MySQL Installation
    3. Tutorial Introduction
    4. Database Administration
    5. MySQL Optimisation
    6. MySQL Language Reference
    7. MySQL Table Types
    8. MySQL APIs
    9. Extending MySQL
    Chapter 4:  Database Administration 279 datadir = /usr/local/mysql/var6 language = /usr/local/share/mysql/japanese user = jani See Section 4.1.2 [Option les], page 186. 4.7.4  myisampack, The MySQL Compressed Read-only Table Generator myisampack is used to compress MyISAM tables, and pack_isam is used to compress ISAM tables.   Because ISAM tables are deprecated,  we will only discuss  myisampack  here,  but everything said about myisampack should also be true for pack_isam. myisampack  works by compressing each column in the table separately.  The information needed to decompress columns is read into memory when the table is opened.  This results in much better performance when accessing individual records, because you only have to uncompress  exactly  one  record,  not  a  much  larger  disk  block  as  when  using  Stacker  on MS-DOS. Usually, myisampack packs the data le 40%-70%. MySQL  uses  memory  mapping  (mmap())  on  compressed  tables  and  falls  back  to  normal read/write le usage if mmap() doesn't work. Please note the following:    After packing, the table is read-only. This is generally intended (such as when accessing packed tables on a CD). Also allowing writes to a packed table is on our TODO list but with low priority.    myisampack  can  also  pack  BLOB  or  TEXT  columns.   The  older  pack_isam  (for  ISAM tables) can not do this. myisampack is invoked like this: shell> myisampack [options] filename ... Each lename should be the name of an index (`.MYI') le.  If you are not in the database directory, you should specify the pathname to the le.  It is permissible to omit the `.MYI' extension. myisampack supports the following options: -b, --backup Make a backup of the table as tbl_name.OLD. -#, --debug=debug_options Output debug log.  The debug_options string often is 'd:t:o,filename'. -f, --force Force packing of the table even if it becomes bigger or if the temporary le exists. myisampack creates a temporary le named `tbl_name.TMD' while it compresses the table.  If you kill myisampack, the `.TMD' le may not be deleted.  Normally, myisampack  exits  with  an  error  if  it   nds  that  `tbl_name.TMD'  exists.   With --force, myisampack packs the table anyway. -?, --help Display a help message and exit.
     

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