How to signal a program that a table has changed?

We are running Oracle on some unix platforms. We would like to have a way of arranging for programs to register an interest in one or more tables, and then having these programs somehow notified when one of these tables changes.

Our Oracle contacts say this will be possible under Version 7, coming out RSN. Unfortunately, I need something by April.

We could of course just have the programs poll the database, but of course this would play hell with the network and oracle engine. I could attenuate the load by writing a server to sit next to the oracle engine and have it do all the polling, and notify its clients when their criteria have been met.

But I'd like to avoid polling altogether, or at least avoid polling requiring i/o. (I wouldn't mind, for instance, using the ptrace calls on the oracle server and poll internal data structures, as this wouldn't have much impact. Better, though, would be to trap calls to an internal "update" function.)

Does anybody have any suggestions as to how I might go about this? Surreptitious suggestions from Oracle folk who know the internals would be warmly welcomed!

Thanks. I can summarize ideas I receive which aren't also posted.

Frederick.

-- 
Frederick G. M. Roeber | CERN -- European Center for Nuclear Research
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