Heikki Linnakangas wrote: > On Fri, 1 Jul 2005, Oliver Jowett wrote: > >> Heikki Linnakangas wrote: >> >>> branch id: Branch Identifier. Every RM involved in the global >>> transaction is given a *different* branch id. >> >> >> Hm, I am confused then -- the XA spec definitely talks about enlisting >> multiple RMs in a single transaction branch. >> >> Can you explain? > > 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.
Ok, I understand that case. What I'm confused about is, for example, 3.3.1 in the DTP:XA spec: > 3.3.1 Registration of Resource Managers > Normally, a TM involves all associated RMs in a transaction branch. (The TM’s > set of > RM switches, described in Section 4.3 on page 21 tells the TM which RMs are > associated with it.) The TM calls all these RMs with xa_start(), xa_end(), and > xa_prepare (), although an RM that is not active in a branch need not > participate further > (see Section 2.3.2 on page 8). A technique to reduce overhead for > infrequently-used > RMs is discussed below. That implies it's valid (in fact, normal!) to enlist many different RMs in the same transaction branch. Am I interpreting that correctly? -O ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
