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(mysql.info)Upgrade


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Upgrading/Downgrading MySQL
===========================

You can always move the MySQL form and data files between different
versions on the same architecture as long as you have the same base
version of MySQL. The current base version is 3. If you change the
character set when running MySQL (which may also change the sort
order), you must run `myisamchk -r -q' on all tables.  Otherwise your
indexes may not be ordered correctly.

If you are afraid of new versions, you can always rename your old
`mysqld' to something like `mysqld'-'old-version-number'.  If your new
`mysqld' then does something unexpected, you can simply shut it down
and restart with your old `mysqld'!

When you do an upgrade you should also back up your old databases, of
course.

If after an upgrade, you experience problems with recompiled client
programs, like `Commands out of sync' or unexpected core dumps, you
probably have used an old header or library file when compiling your
programs.  In this case you should check the date for your `mysql.h'
file and `libmysqlclient.a' library to verify that they are from the new
MySQL distribution.  If not, please recompile your programs!

If you get some problems that the new `mysqld' server doesn't want to
start or that you can't connect without a password, check that you don't
have some old `my.cnf' file from your old installation!  You can check
this with: `program-name --print-defaults'.  If this outputs anything
other than the program name, you have an active `my.cnf' file that will
affect things!

It is a good idea to rebuild and reinstall the `Msql-Mysql-modules'
distribution whenever you install a new release of MySQL, particularly
if you notice symptoms such as all your `DBI' scripts dumping core
after you upgrade MySQL.

Upgrading-from-3.22
Upgrading from a 3.22 version to 3.23
Upgrading-from-3.21
Upgrading from a 3.21 version to 3.22
Upgrading-from-3.20
Upgrading from a 3.20 version to 3.21
Upgrading-to-arch
Upgrading to another architecture

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