Options can be combined, for example tmem cat will reset compiled styles, the table cache and the attribute cache. The tmem * option shouldn't usually be needed but it could be useful to reclaim as much memory as possible, especially if more cache items are added later.

Resetting compiled styles is useful if something changes which would affect the compiled result. The most likely occurrence of this is when setting the Speed option of thetdpref dialog (see menu option Document > Preferences > Document > Speed) to Compile x-counter and string indices. Whenever index variables are added or changed you should use tmem c to have any compiled styles recompiled with new values.