Ok, first, in the original example of select only, why would you "rollback"
?? You haven't changed any data in the database to "undo" ?? You should
always commit. Rollback should be used for just as it sounds. That is to
undo some changes that were made to the data in the database. Select's don't
change anything, right, sooooo, why rollback.
Now, I had asked a question a year or two ago about rollbacks, along the
lines of what Jason is indicating below. What happens if you do a select and
then rollback (you've changed nothing, data related, in the database.) Ann
replied (pre FB days) that the engine is/was smart enough to realize that
nothing had changed and actually do a commit. We do really, really, really
time critical stuff with our databases (realtime and very fast), so speed is
important. Ann said that it does take a little longer for the engine in this
case. But anyway, back to the original question. Select's don't change data,
so commit, don't rollback.

Best regards,
Fred Wilson
SE, Bell & Howell
fred.wilson@... <mailto:fred.wilson@...>



-----Original Message-----
From: Jason Chapman (JAC2) [mailto:jason@...]
Sent: Wednesday, February 13, 2002 9:56 PM
To: ib-support@yahoogroups.com
Subject: Re: [ib-support] Transaction and time keepping program


I believe that rollbacks do not get cleared from the TIP (transaction
information page?) until you do a sweep. Now I don't know exactly what the
exact effect of this is (e.g. garbage collection stops short of clearing all
possible back versions), but the net effect is that the oldest transaction
does not move forward until you do a sweep.

If the difference between your oldest transaction and your current
transaction is too great then performance will degrade (I currently have a
DB that the difference between oldest and active = 59,000,000).

We don't do sweeps at the moment as I can not get clarification that the
sweep bug (5.x) was solved for 5.6. I posted a question about this a month
or so ago (ann, paul...).

I emphasise "I believe" - already this week I have got it wrong in the forum
(15,2).

From this I deduce that commits are "better" than rollbacks if you don't
regularly sweep the database.


JAC.

> On Thursday 2002-02-14 at 09:06:49 +0800, Frank Wang wrote:
> Don't know the tehnicalities, but I've heard COMMIT is supposed to be
> better (must be to do with housekeeping, as someone mentioned).

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