tmp_table_size Question

[tubeman]

Hi,
I have about 20 sites on a server and its using Innodb according to the MySQL tuning, crons are optimized.Server has total 12 GB RAM and 90% is being used.I checked with admin and he says that the setting for:

max_heap_table_size = tmp_table_size = 128 MB is too high and that's why its eating up the RAM.Is it safe to lower this setting to 32 or 64 on high traffic sites? Any advice as to what to do?

Regards,

[admin]

Those changes are reversible in a flash, so you can set as you want, check results, leave it or roll it back if you don't like it.