> I don't know of any SQL databases that allow non-blocking lock requests.
>
Informix has all kinds of non blocking locks:
return "record locked" at once
return "record locked" after a specified timeout
wait for the lock indefinitely
To supply this behavior it has the following statements:
set lock mode to not wait; -- return immediately with error
-- if record already locked
set lock mode to wait 10; -- wait at max 10 seconds
set lock mode to wait; -- wait indefinitely
Dirty read isolation has actually nothing to do with the wanted feature.
Andreas