Hi Helen,

Thanks for that - it sorted us out.

Cheers,

Ryan Thomas
TransActive Systems

P: (02) 4322 3302
F: (02) 4325 1141
E: ryan@...
W: http://www.transactive.com.au/

> -----Original Message-----
> From: firebird-support@yahoogroups.com
> [mailto:firebird-support@yahoogroups.com] On Behalf Of Helen Borrie
> Sent: Friday, 19 August 2005 1:43 PM
> To: firebird-support@yahoogroups.com
> Subject: Re: [firebird-support] Transaction isolation and server type
>
> At 10:28 AM 19/08/2005 +1000, Ryan Thomas wrote:
> >Hi All,
> >
> >I'm not sure if this is more for the IBO list or the fb-support list.
> >
> >We are running a system that uses two different transactions
> on the client
> >application - one for read-only and one for read-write
> operations. Our
> >transaction isolation settings were set to tiCommitted for
> both of them.
> >This works fine on the vast majority of our customers - which are all
> >running super-server.
> >
> >Last night we ran into a problem with our only customer who
> is running
> >classic server -
>
> >whenever nearly any query is run we get a lock conflict on
> >no wait transaction (as if one of the transactions is set to
> tiConsistency).
>
> What exactly do you mean by "nearly any query"? Are you getting lock
> conflicts on the SELECT that is in the read-only transaction,
> or only on
> submitting the DML statements in the read-write transaction?
>
> >
> >Setting the read-only transaction to tiConcurrency resolves the lock
> >conflict but brings in a bunch of refresh issues (i.e. to display the
> >changes made by the rw transaction).
>
> Of course. The read-only transaction must be in Read
> Committed, so as not
> to make that transaction "interesting", from a garbage-collection POV.
>
> What is of concern for running two Read Committed
> transactions side-by-side
> is the visibility to one transaction of uncommitted work from
> the other.
> The transaction attribute of interest here is RECORD
> VERSION/NO RECORD
> VERSION. Since you are using IBO, pick up the documentation
> in the Help
> file for the RecVersion property. It gives a very telling
> account of what
> you have described here, if RecVersion on your read-only
> transaction is
> false and LockWait is false. It will prevent any other
> transaction from
> making changes, including the dummy change that occurs when
> you use IBO's
> statement-level PessimisticLocking feature.
>
> Needless to say, similar conflict will occur when other users
> attempt to
> add or update records from *their* transactions.
>
> >
> >Is there some sort of configuration setting that needs to be
> set on classic
> >server?
>
> There's no difference as far as transaction-by-transaction control is
> concerned - it's the same server in different outerwear. If the
> application code is identical then the "different behaviour" is
> coincidental, attributable to variations in usage.
>
> >
> >Also, I have google'd for a build of SS for FreeBSD but
> can't seem to find
> >one - are there any issues with building SS under FreeBSD
> that anyone knows
> >of?
>
> Yes. Building from source isn't in the Firebird-support
> bailiwick but, as
> far as I can tell, there has never been a released build of
> SS for FreeBSD
> because of threading issues that couldn't be resolved. You
> might like to
> search the firebird-devel archives for recent activity by the FreeBSD
> afficionados, regarding attempts to build Fb 2 on FreeBSD
> 5.x. On the
> whole, they are the same people who attempted the Fb 1.5 SS
> builds, so it
> would be appropriate to ask the pertinent questions in that forum.
>
> ./heLen
>
>
>
>
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