I understand what this does but in what scenario would you use this option.
Meaning site is slow have a lot of valid visitors or what?
Why is it using memory to begin with?
In 2007 with version 7.1.0, the those TEMPORARY high-transaction tables were moved from disk storage to memory storage. The idea behind this was probably due to the tables being temporary, and that they had a high volume of read/writes. Ram generally is faster than physical hard disk storage, especially in 2007 when the change was made.
