Intent LOCK

Art S. Kagel said: "There is no explicit SQL 'lock row' command. SQL transactions take an exclusive lock on each row which has been updated and an intent lock on any row which is fetched with the intent of updating later. An intent lock will prevent any other user from acquiring an exclusive lock but will not prevent anyone from acquiring another intent lock. Intent locks are promoted to exclusive locks when the row is updated. This is the only locking scheme that is available. " I think there is no one in the informix-world, who knows exactly what INTENT LOCKS are. Someone think, that it is to prevent other Users from altering tables which have rows locked, Art means, that INTENT LOCKS are "promoted" to Exclusive LOCKS, if the row is updated. What i'm confused about is that there may be more than one INTENT LOCK on a table: User A: Update table1 ===> IX on the Table If this IX-LOCK is for preventing other users from altering the table or place an exclusive lock on the table, then this is enough to see for the next processes, that they cannot do so. But User B: UPDATE table1 =========>> IX on the same table SO: what is the sense of an INTENT LOCK? And another question: Why do Informix have no documents, which describe in detail the INTENT LOCKS (training manuals mention INTENT LOCKS, but they don't exclaim it very good)? Christian -------------------==== Posted via Deja News ====----------------------- http://www.dejanews.com/ Search, Read, Post to Usenet