Tom, good comments. I do disagree on one point though: > > In practice, it's only two. The "don't know" has the exact > same behavior as > the "cannot commit". So, as with app server managed OCC, the > programmer has > to deal with a single failure scenario. I may be being overly pedantic, but I think that there are differences in some circumstances. In the "don't know" case (i.e. the necessary history has been aged out) you might potentially fall back on less efficient checks to determine an exact answer, e.g. the kind of explicit verification discussed in other threads. Whether it is worth doing so will depend on the exact semantics and value of the tx. Also there are circumstances in which it is worth telling the user to try again after a "don't know" but not after a "can't commit" - think substitutable resources versus unique resources. However, I will readily agree that in a GREAT MANY real world applications, treating a "don't know" the same as a "cannot commit" will give the appropriate application behavior. Still, its something that a designer has to consider, especially in a scenario of high concurrency > Also, the "don't > know" scenario > results from a database not properly configured to handle the > concurrent > load. This is a configuration (tuning) issue, not a normal > failure scenario > (IMHO). Yes... and no :-> Certainly the "don't know" comes from the database not being configured to handle the concurrent load, but in the real world the concurrent load may be unpredictable (or have load spikes that it is inefficient to configure for in normal usage). Either way, dealing with the failure scenario ends up with the developer, whose program has to shield the user from a completely incomprehensible error message... regards, Carl =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff EJB-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
