You must change the location of MySQL’s temporary folder which is ‘/tmp’ in most cases to a location with a bigger disk space. Change it in MySQL’s config file. Basically your server is running out of disk space where /tmp is located.
Sometimes when this error happens with temp tables: #126 – Incorrect key file for table ‘/tmp/#sql_64d_0.MYI’; try to repair it It can be because the /tmp folder is running out of space. On some Linux installations, /tmp is in its own partition and does not have much space – big MySQL queries will fill it … Read more
Every Time this has happened, it’s been a full disk in my experience. EDIT It is also worth noting that this can be caused by a full ramdisk when doing things like altering a large table if you have a ramdisk configured. You can temporarily comment out the ramdisk line to allow such operations if … Read more