I've recently noticed a table in mySQL server taking up lots of disk space(90+G) and wish to optimise it to make it perform better. However, my current partition isn't big enough to accommodate the temporary files which will be created during the optimisation, so I wish to move the tmpdir, which stores the temp files, to an external hard disk. I'm on a Mac, so I went to where XAMPP was installed: /Applications/XAMPP/xampppfiles/etc/ and location the example my.cnf file. I copied it out to my desktop, edited the tmpdir path to my external hard disk, and deposited this file into /etc/ as instructed by the file to set "global options". I then restarted my computer and launched the mySQL server, then went ahead to do the optimisation, but noticed that the same thing happened before, that the main hard drive was filling up on space really quickly thanks to the temp files. Please help. Thanks.