Hello I am a newcomer from VB and have read almost all of the "innodb or myisam" and "mysql tuninig" threads. Database is InnoDB (Except those 2-3 table which is MyISAM and few MEMORY) based on this. But MySQL hangs every few hours with lots of "Waiting for table level lock". Those queries who are waiting are: Code: SELECT post.* , bb_code_parse_cache.parse_tree AS message_parsed, bb_code_parse_cache.cache_version AS message_cache_version, user.* .... and Code: INSERT INTO xf_session_activity (user_id, unique_key, ip, controller_name, controller_action, ... Any Idea why this happens? I think this table level lock is because of some queries which are related to those non-InnoDB tables. Should I switch xf_session_activity from MEMORY to InnoDB ?