( Downgrading

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 2.11 Downgrading MySQL
 This section describes what you should do if you are downgrading to an
 older MySQL version in the unlikely case that the previous version
 worked better than the new one.
 If you are downgrading within the same release series (for example, from
 4.0.20 to 4.0.19) the general rule is that you just have to install the
 new binaries on top of the old ones. There is no need to do anything
 with the databases.  As always, however, it's always a good idea to
 make a backup.
 The following items form a checklist of things you should do whenever
 you perform an downgrade:
    * Read the upgrading section for the release series from which you
      are downgrading to be sure that it doesn't have any features you
      really need.   Upgrade.
    * If there is a downgrading section for that version, please read
      it, too!
 You can always move the MySQL format files and data files between
 different versions on the same architecture as long as you stay within
 versions for the same release series of MySQL. The current production
 release series is 4.1.
 If you downgrade from one release series to another, there may be
 incompatibilities in table storage formats. In this case, you can use
 `mysqldump' to dump your tables before dowgnrading.  After downgrading,
 reload the dump file using `mysql' or `mysqlimport' to re-create your
 tables.  See  Upgrading-to-arch for examples.
 The normal symptom of a downward-incompatible table format change when
 you downgrade is that you can't open tables.  In that case, use the
 following procedure:
   1. Stop the older MySQL server that you are trying to downgrade to.
   2. Restart the newer MySQL server you are trying to downgrade from.
   3. Dump any tables that were inaccessible to the older server by using
      `mysqldump' to create a dump file.
   4. Stop the newer MySQL server and restart the older one.
   5. Reload the dump file into the older server. Your tables should be


* Downgrading to-4.0          Downgrading to 4.0
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