We do not recommend to change MySQL’s innodb_log_file_size parameter, but if you need to, you can’t just change the parameter it in the my.cnf file and restart the server.
If you do, InnoDB will refuse to start, because the existing log files don’t match the configured size.
To do so, you can follow these steps.
Please back up your mySql database before attempting to make any such changes.
Shut the server down cleanly and normally.
Move away (don’t delete) the log files, which are named ib_logfile0, ib_logfile1, etc.
Check the error log, to ensure there was no problem shutting down.
Restart the server and watch the error log output carefully.
You should see InnoDB print messages, saying that the log files don’t exist. It will create new ones and then start.
Verify that InnoDB is working, before deleting the old log files.