Online : key value locked ?

Hi, i have a problem accessing a Informix-Online-Database (Version : 5.03.UC1) : Description : The Server is accessed via program by 2 Clients, both are in transaction and work on the table ap; Isolation is set to dirty read. ap_idx is a column of ap, type serial, there is a unique index on ap_idx. Client1 : delete from ap where ap_idx = 2500 but stays in transaction ! Then : Client2 : delete from ap where ap_idx = 2499 Client2 : insert into ap values (2499,.......) or any other value < 2499 works. But : Client2 : delete from ap where ap_idx = 2501 Client2 : insert into ap values (2501,.......) or Client2 : insert into ap values (0,...) for automatically the next Index or any other value > 2501 ends up with errormessage -240 : Could not delete row ISAM-Error -144 : key value locked As far as i have understood the documentation this Error should occur, if i try to insert data into the table with a value in the "Unique-Index-Column", which isnt there at the moment, but was deleted in a transaction, that is still open and could therefore reappear, if this transaction is rollbacked, in the above example ap_idx = 2500, but in this case i get the ISAM-Error -107 : Record is locked ! Using the database on Informix-SE i don't have these problems ! Why has deleting of a row in a table any effect on inserting or deleting of other rows with higher values in the "Unique-Index-Column" ? Are ther any Informix-Online settings, which enable the behavoiur of the Informix-SE ? I am very thankful for any ideas or comments concerning the problem. Bye and thanks.. Michael ---