[Q] Concurrency/Locking Technique Problem

I am new to Informix and I've reached the problems in design of application for concurrent database use. Would somebody please to answer the following questions: 1. Does the ISOLATION LEVEL work outside a transaction? I tried CURSOR STABILITY ISOLATION LEVEL and have got a situation: a promotable/exclusive lock can be obtained by the 1st user with update cursor FETCH (in transaction) while a shared lock already placed by the 2nd user with select cursor FETCH (with no transaction) -- for the _same_ record. (Manual says the promotable lock can't lay on any other lock.) 2. What is the best way to restrict user to edit record while another user is already editing this record? (avoiding long transactions, but 'editing' can take a moment) 3. What issue (if any) can be used for studing OnLine v.5 concurrency tips (just direct me: books, magazines, FTPs ...) My evironment is: OnLine 5.0, 4GL, database is not ANSI-complient. Thanks in advance. -- Sergei Davidov Rosan-Dovira, Lviv, Ukraine +7(0322)21-65-15 sdav@rdovira.lviv.ua