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How do I prevent TOraSession from implicit commit?
Posted: Tue 30 Aug 2011 14:31
by William
If an application is stopped or crashes while TOraSession is in transaction
DML changes are saved anyway.Is there a way to prevent TOraSession
from committing these changes ? Both TOraSession and TOraTable AutoCommit properties are set to false.
I can see the same topic, but can't see the answer.
Posted: Wed 31 Aug 2011 08:56
by AlexP
Hello,
You should use the TOraTransaction component to solve this problem, and you should set it its DefaultCloseAction property to taRollback (it's default value is taCommit by default).
Posted: Wed 31 Aug 2011 13:34
by AGOSSELIN
Hi,
In your last answer in the following link you seem to have an other solution ?
http://www.devart.com/forums/viewtopic. ... t=implicit
Thanks,
Posted: Wed 31 Aug 2011 14:32
by lior
Hello,
At the time I asked AlexP about it, he wasn't aware of the problem.
I hope that in future release TOraSession won't implicitly commit changes.
Posted: Wed 31 Aug 2011 14:40
by AGOSSELIN
Hi Lior,
Did you add TOraTransaction everywhere to fix the problem or you find an easier solution ?
Like you, we have a lot of place to change and we still hope to find an other way.
Thanks,
Posted: Wed 31 Aug 2011 14:48
by lior
Hello AGOSSELIN,
Unfortunately I will have to add TOraTransaction everywhere.
Posted: Thu 01 Sep 2011 12:04
by AlexP
Hello,
We cannot change the default value to taRollback, because many users got used to such behaviour. One of the ways to solve this problem is to create your own class that is a descendant of TOraSession and change the DefaultTransaction.DefaultCloseAction property to taRollback.
Posted: Thu 01 Sep 2011 14:16
by lior
Hello Alexp,
I have no problem with TOraTransaction.DefaultCloseAction defaults to taRollback.
I think that if TOraSession.AutoCommit=False and it manages the transaction (TOraSession.StartTransaction without TOraTransaction) it should not save changes to the database before TOraSession.Commit command.
Posted: Mon 05 Sep 2011 12:32
by AlexP
Hello,
The AutoCommit property is responsible for the “immediate” commit of data into a table, i.e. if this property is on, it will be impossible to perform rollback after executing the following code:
Code: Select all
OraSQL.SQL := 'DELETE FROM Dept';
OraSession.AutoCommit := True;
OraSQL.AutoCommit := True;
OraSQL.SQL := 'DELETE FROM Dept';
OraSQL.Execute; // delete all records, commit is performed
OraSession.Rollback; // couldn't restore deleted records
If transaction is started explicitly
the AutoCommit property does not influence saving data, and data is saved to the server only on the explicit calling of
, on closing a session with an active transaction, or on destroying a component (in two latter cases the TOraTransaction.DefaultCloseAction property should be set to taCommit).
Posted: Mon 05 Sep 2011 13:01
by lior
ODAC equivalent to TDatabase is TOraSession. They both can start,commit or rollback a transaction.
However, If I want to make sure crashed application (Alt+Ctr+Del etc) don't save transaction changes, I have to add and connect TOraTransaction to each TOraSession. This complicates the conversion.
Posted: Tue 06 Sep 2011 12:49
by AlexP
Hello,
By using the (Ctr+Alt+Del) you can end a task in the following two ways:
1- End Task
2- End Process
In the first case, the application will close on getting the WM_CLOSE, and its data will be committed. The second option is equivalent to application crash, data will not be committed.
In order not to add TOraTransaction to each TOraSession component, you can use your own component inherited from ToraSession, as I wrote earlier.
Posted: Tue 06 Sep 2011 13:21
by lior
Hello,
You wrote earlier "Create a descendant of TOraSession and change the DefaultTransaction.DefaultCloseAction property to taRollback".
I don't have the source yet.Do you say thay I should create a TOraTransaction component inside the TOraSession descendant or is there a built in privete/protected DefaultTransaction property?
Posted: Tue 06 Sep 2011 14:57
by AlexP
Hello,
To prevent data from being automatically committed, you need to override the TOraSession constructor by setting the DefaultTransaction.DefaultCloseAction property to taRollback. The component's code is provided below:
Code: Select all
unit RollbackOraSession;
interface
uses
SysUtils, Classes, DB, DBAccess, Ora, CRAccess;
type
TRollbackOraSession = class(TOraSession)
public
{ Public declarations }
constructor create(Owner: TComponent);override;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Oracle Access', [TRollbackOraSession]);
end;
{ TRollbackOraSession }
constructor TRollbackOraSession.create(Owner: TComponent);
begin
inherited create(Owner);
DefaultTransaction.DefaultCloseAction := taRollback;
end;
end.