> > > What happens to the garbage collection when it rolls over? I was under
> > > the impression that this limit was a show-stopper that you had to
> > > backup-restore pre-emptively to prevent.
> > >
> > > Adam
> >
> > a 24x7 system where you don't do regular garbage collection backups?
> > Alan
> >
>
> Of course this happens nightly, but the oldest transaction will end up
> being significantly greater than the current transaction when it rolls
> over. I can't see how the MGA mechanisms can work if it simply cycles
> over.
>
> To quote Helen "bad things will happen" when the Transaction ID overflows.
>
> (The Firebird Book p512 for details)
>
> Adam

of course this could be an issue..
but in a web environment, how does the oldest Transaction be much greater
than the current (next). Each page delivered is committed or explictly
rolledback. There are no long running transactions.

I've just check my web DBs and this is typical.

Oldest transaction 1079651
Oldest active 1079652
Oldest snapshot 1079652
Next transaction 1079653
Creation date Nov 15, 2005 21:53:41

a diff of 1 between oldest and next...
Now lets do some sums
April 14 to Nov 15 last year = 150 days
therefore 7200 transactions per day
is that high? is that low? - high to some, low to others, very low to yet
others.
5 Transaction per minute
Lets dream up a very heavy website
50 Transactions per second (can your CPU and HD handle it?)
4 million Transactions per day
Total available
2,147,483,648
= 536 days
Not long at this rate....
For me... at my rate.... it's 300,000 days = 800 years.
I don't think I'm in much danger....
Someone is asking questions about a major application for a Banking System -
they want 5 million Transactions per month - that's 2 per second (not 50) or
35 years.
Someone else is arguing that 700,000 per day is large... that's 8
Transaction per second
that's 8 years life before a backup/restore.
Bottom line - know your transaction rate and act accordingly.... agree?

Alan