Currently we can not see any statistics about cost of such actions as truncationg GTT and cleaning of temp blobs that take place after commit/rollback.
Discussion about this can be found here (in russian): http://www.sql.ru/forum/actualutils.aspx?action=gotomsg&tid=860810&msg=10871916

2 hvlad: it seems to me that no any change since that topic, isn't ?