> Lowering the number of transactions can definitely improves processing
> speed a lot, especially in case of high server load.
> Remember that a 2 resouces 2PC typically requires at least 5 disk
> forces (including DB and TM: 2 per resource + 1 for TM) while a simple
> 1PC requires only one. The potential benefit could be high but maybe
> Firebird's MGA lowers that gain, I don't know.

That will be at least one TIP page flush per transaction state change
(prepared/committed). And in case of 1PC only one TIP page flush.

> Limiting isSameRM is I think a good candidate fix to be implemented before
> the final Jaybird2 release.

Ok, we seem to be in agreement.

> On the other hand, having this optimization is nice to have, just like
> it would also be nice to see support for XA_RDONLY. Both can be
> considered very low priority and only implemented if the DB engine
> provides necessary help.

Would you be interested to specify what optimization would be nice and
define test cases for them? We would try to address them in JayBird 2.2
(JayBird 2.1 should be release with events support).

> Thanks a lot to both of you Romand and David for answering my
> question. You already did a great job by providing us the only open
> source DB truly supporting JDBC XA.

Do you have some more information about this? What about PostgreSQL 8 or
MySQL 5?

Roman