Locking, please help.

Hello all, I am currently having some problems with locking. My problem simplified seems to be this, as far as I can tell: Application 'A' does large update of a high use table 'x' like this - begin work foreach insert or update on table x end foreach commit work Application 'B' does simple insert into high use table like this - begin work insert on table x commit work So, while App A does inserts/updates, App B error's out like this - SQL statement error number -271. Could not insert new row into the table. SYSTEM error number -154. ISAM error: Lock Timeout Expired. Is it a general rule that if you use a transaction to do a update/insert on a table, no other process can insert into the table until the transaction is completed? Or, is it because I am using page level locking and some rows are getting locked that shouldn't be? If it is page level locking, what type of perfomrance degradation might be associated with altering a table to row level locking? I have the applications in question 'set lock mode to wait 20'. My apologies if this is a stupid question. Oh, IDS 7.30.UC6 on sun os 5.6. Thanks in advance. Olaf