joserudi - Instead of number use [find]. It will execute command on all entries in list;
History clear function does not work with database. If you do something in UM, then you can undo this function by using history. History could grow up to ~150MB in RAM memory. After reboot it still would be clear. Now you can clear this history and get rid of used RAM. For example, if you have a UM on mipsbe with ~100MB of RAM, then there is pretty good chance that after a while device will run out of memory.