To change the number or the size of your InnoDB
redo log files, perform the
following steps:
If innodb_fast_shutdown is
set to 2, set
innodb_fast_shutdown to 1:
mysql> SET GLOBAL innodb_fast_shutdown = 1;
After ensuring that
innodb_fast_shutdown is not
set to 2, stop the MySQL server and make sure that it shuts
down without errors (to ensure that there is no information
for outstanding transactions in the log).
Copy the old log files into a safe place in case something went wrong during the shutdown and you need them to recover the tablespace.
Delete the old log files from the log file directory.
Edit my.cnf to change the log file
configuration.
Start the MySQL server again. mysqld sees
that no InnoDB log files exist at
startup and creates new ones.