Re: Big 7.4 items

darren(at)up(dot)hrcoxmail(dot)com wrote:
> >
> >
> > Darren, can you clarify this? Why does it send that message? How does
> > it allow commits not to wait for ordered writesets?
> >
>
> There are two channels. One for total order writesets
> (changes to the DB). The other is simple order for
> aborts, commits, joins (systems joining the replica), etc.
> The simple channel is necessary, because we don't want to
> wait for total ordered changes to get an abort message and
> so forth. In some cases you might get an abort or a commit
> message before you get the writeset it refers to.
>
> Lets say we have systems A, B and C. Each one has some
> changes and sends a writeset to the group communication
> system (GSC). The total order dictates WS(A), WS(B), and
> WS(C) and the writes sets are recieved in that order at
> each system. Now C gets WS(A) no conflict, gets WS(B) no
> conflict, and receives WS(C). Now C can commit WS(C) even
> before the commit messages C(A) or C(B), because there is no
> conflict.

Oh, so C doesn't apply A's changes until it see A's commit, but it can
continue with its own changes because there is no conflict?

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073