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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
accessible.
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