What I like about DB2 lock system is to have hard lock mechanism.For example,a application must wait to refer the data row while other application is updateting the same row.If the time set LOCKTIMEOUT parameter is filled during waiting update,a application have to be aborted.Some developpers hate this supecification.But I think it's nature,is needed for DBMS.So I feel strange oracle provide previous row if application need to select data which is being updated.On the other hand,I know oracle"s lock system has a merit that give aplpications and developpers powerful concurrency.
The best way is to understand the lock system differences among databases.
