On Fri, 1 Jul 2005, Barry Lind wrote:
I oversimplified a bit. The TM *can* enlist multiple threads of control
(= connection in JTA) to the same transaction branch. That's called
"tightly-coupled threads", and they should then be treated as one
local transaction in the RM. The calls will look like this:
conn1.start(xid1, TMNOFLAGS);
...
conn2.start(xid1, TMJOIN);
...
conn1.end(xid1, TMSUCCESS);
...
conn2.end(xid1, TMSUCCESS);
connX.prepare(xid1);
connX.commit(xid1, false);
conn1 and conn2 must share locks and see each others changes. They
mustn't deadlock each other. The JDBC driver can implement this in a
very
straight-forward way by using the same physical connection for both
conn1
and conn2. Note that there's only one prepare, and it can be issued
using
any connection.
In your example above couldn't conn1 and conn2 be running in two
different JVMs? And thus your statement that 'the JDBC driver can
implement this in a very straight-forward way by using the same physical
connection' would not be true. I can't see a way for two JVMs (possibly
on different client machines even) to share the same physical
connection.
I can't immediately think of a reason why they couldn't run in two
different JVMs, but I also can't think of a reason why anyone would want
to do that. Can you give a use case for that?
Also, it would require an application server that would support that, and
I don't think there is any.
- Heikki
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