To change the number or the size of your
redo log files, perform the
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.
my.cnf to change the log file