Could calling Tquery.Commitupdates before calling a Tdatabase.Commit
cause any issues, cause other than the fact the bde driver flags is null
my code does as suggested.


Martin Dew

Senior Developer

Adastra Software Ltd.

Unit 4, Eurogate Business Park, Ashford, Kent TN24 8SB

Tel: (01233) 722700 Fax: (01233) 722701 www.adastra.co.uk


-----Original Message-----
From: Johannes Pretorius [mailto:johannes@...]
Sent: 03 December 2003 09:49
To: firebird-support@yahoogroups.com
Subject: RE: [firebird-support] Who's guilty?---


For Deadlocks I have changed my Flags to be 4608 and uses the
StartTransaction and Commit before a re-read of the data as this
connection type makes that you don't see any new transactions until you
have commit a transaction. It makes the change smaller depending of
coarse on what you app does.


My Commit Retain is also false, but I believe more advice on that can be
given from people like Helen on this. For me it works as False.

If you have TQuery components that does NOT have Cached updates then
they are trying to use or REQUESTLIVE that can fail and is not adviced
as this is like have a TTABLE or on the Update Events do direct updates.
NOW with these direct updates you can have problem as they are possibly
NOT in a transaction.

I personally believe in Cached updates as that keeps the network traffic
to the min. and only uses the Server when everything is ready. You also
seem to have more control. So I would advice to try and move these
TQueries that is used for UPDATES but without Cached update over to use
Cached updates. This will allow you to use the Tdatabase.ApplyUpdates
that is a well controlled manner of doing it.

How your transaction is suppose to be is something like :
A) Start Transaction
B) Do ApplyUpdates for All relevant queries if they are in a loop
C) Commit Transaction

IF Commit was successful then
D) Flush Query internal buffer with CommitUpdates ELSE
D) Rollback

Hope this helps.

Johannes

At 09:08 03/12/2003 +0000, you wrote:

>
>Once again, thanks to you all for offering advice..
>
>Our bde settings are set to COMMIT RETAIN=FALSE
>
>The driver flags where null inside the
>BDE/Configuration/Drivers/Native/Interbase - should I use 4096 here
>with COMMIT REATIN=FALSE or TRUE ??
>
>In our app we call a Tdatabase.StartTransation
>
>Then call Tquery.ApplyUpdates and Tquery.CommitUpdates on any dataset
>using CachedUpdates=True and then call Tdatabase.Commit with an
>exception handler calling a TDatabase.Rollback if an exception is
>raised. Not all of our queries inside the app use Cached Updates. I
>unfortunately inherited this application from another developer, so am
>unaware of exactly why he chose to do it this way.
>
>TIA
>
>Martin
>
>
>-----Original Message-----
>From: Johannes Pretorius [mailto:johannes@...]
>Sent: 03 December 2003 05:40
>To: firebird-support@yahoogroups.com
>Subject: RE: [firebird-support] Who's guilty?---
>
>Good day
>\=-\=-\=-\-=-
>If I may ask why don't you use the
>TDatabase.ApplyUpdates([query1,query2,...]);
>function ?
>
>This will make sure that ALL cahced updates are forced to the database
>and does it all in a transaction, if anything fails, ALL rollsback and
>returns to you. You can wait for 2 seconds and try again for instance
>?,.,.
>
>In short using the TDatabase.ApplyUpdates will insure that your
>Transactions is CLOSED correctly and if you use the DRIVER_FLAGS 4608
>then doing a TDatabase.StartTransaction and then immediatly a
>TDatabase.Commit before a re-read of a Query will force all previous
>transactions out and open you up for the newly added entries.
>
>Here is some info on the DRIVER FLAGS
>//========== SNIP START ==============
>Roles
>-----------
>InterBase allows users to log in by specifying a role.
>ROLE NAME is a new BDE configuration parameter that allows BDE clients
>to pass a role name. ROLE NAME can also be passed as an optional
>parameter when using a TDatabase component (Delphi and C++Builder).
>
>This information supersedes that in the InterBase 5.5 Operations Guide,

>which indicates that the BDE has no property for specifying a role

name.

>
>Transaction Isolation Levels & InterBase
>----------------------------------------------
>By adding 4096 to the setting of DRIVER FLAGS in the Borland Database
>Engine (BDE) configuration, you can specify that the InterBase SQL
>Links driver should use soft commits. Soft commits are a feature of
>InterBase that let the driver retain the cursor when committing
>changes. Soft commits improve performance on updates to large sets of
>data. When not used, the BDE must re-fetch all the records, even for a
>single record change. With soft commit the cursor is retained, and a
>re-fetch is not needed. The soft commit property corresponds to the
>COMMIT RETAINING transaction option in the InterBase documentation.
>
> DRIVER FLAGS Isolation level Commit type
> ------------ --------------- ------------
> 0 Read committed hard commit
> 512 Repeatable read hard commit
> 4096 Read committed soft commit
> 4608 Repeatable read soft commit
>
>The 4096 driver flag bit only affects implicit transaction behavior.
>Use the COMMIT RETAINING property to control the default commit
>behavior of explicit transactions.
>
>Explicit transactions
>---------------------------
>The new BDE configuration parameter COMMIT RETAIN allows explicit
>transactions to use soft commit. The new database property
>dbCOMMITRETAIN also does this. Only explicit transactions are affected.
>The existing driver flags are still valid for explicit transactions.
>
> COMMIT RETAINING = TRUE calls isc_commit_retaining()
> COMMIT RETAINING = FALSE calls isc_commit_transaction()
>
>Transaction WAIT
>----------------------
>Currently, the InterBase SQL Links driver uses NOWAIT when resolving
>lock conflicts and returns an error immediately if there is a resource
>conflict. Setting the WAIT ON LOCK configuration parameter allows SQL
>Links to use WAIT on InterBase transactions. This can also be done by
>setting the r/w database property dbWAITONLOCK to TRUE.
>
>//============== SNIP END ================
>
>Otherwise is the BDE SQLPASSTHRU MODE = SHARED AUTOCOMMIT.
>
>I had problems that if this was set to SHARED NOAUTOCOMMIT that if a
>app dies that the record is logged for a while, but this will create
>Deadlock problems anyways.
>
>I hope this helps in anyway
>
>Johannes
>
>At 11:23 02/12/2003 +0000, you wrote:
>
> >The app uses the BDE to connect to the database and do its work.
> >
> >We call TDabase.Commit inside a try except block, the exception
> >handles
>
> >calling Tdatabase.Rollback.
> >
> >I am not too sure what you mean by autocommit and hard commits.
> >
> >The databases have forced writes enabled, and we seem to handle
> >ApplyUpdates, CommitUpdates in the Tquery objects, then call a
> >Tdatabase.Commit.
> >
> >Is there something else we should be doing, if so please please
> >please tell me as my customers are also rather annoyed with having to

> >be taken
>
> >down (they are 24/7 medical operations) to backup and restore....
> >
> >Thanks for any help..
> >
> >-----Original Message-----
> >From: Helen Borrie [mailto:helebor@...]
> >Sent: 02 December 2003 11:16
> >To: firebird-support@yahoogroups.com
> >Subject: RE: [firebird-support] Who's guilty?
> >
> >At 09:36 AM 2/12/2003 +0000, you wrote:
> > > I have similar issues with some of my sites using IB5.6 and
> > >IB6.0.2.0, I cannot replicate this in my test rig, and I have
> > >checked
>
> > >my commiting code numerous times to make sure I am always calling
> > >either a .commit or a .rollback ,
> >
> >I suppose you do understand that, if commit fails, your application
> >will have to handle the failure...
> >
> >..and that Autocommit prevents the record versions from the involved
> >transactions from being made "uninteresting"...
> >
> > >but I get I huge gaps in transaction statistics, I cannot do a
> > >sweep as
> >
> > >the gap is not between the OIT and OAT (see example) so my only
> > >option is a backup and restore. I have tried IB_AFFINITY to set it
> > >to
>
> > >one processor in the dual processor machine, I have also had the IT

> > >team turn off hyperthreading in the bios, all to no avail.
> > >
> > >OT 566738
> > >OAT 566739
> > >NT 940551
> > >OS 564916
> > >
> > >After checking this weekend the OT,OAT and OS have not moved from
> > >above, but the NT is now more than a gap of 1 million to these
> > >other
> >stats..
> >
> >1 million Autocommits and no hard commits?
> >
> >/heLen
> >
> >
> >
> >
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