Re: IDS 11 optimistic locking

Hi Clifton, Keep in mind this is for reads only. If you have two writers: Session A =========== begin work; update customer set fname="FRED" where fname="Fred" Session B =========== begin work; update customer set fname="fred" where fname="Fred" They will still wait the same as they have always waited. Same goes for inserts. ----- Original Message ---- From: Clifton Bean <cbean@ctm.com> To: classics@iiug.org Sent: Thursday, November 15, 2007 8:10:38 AM Subject: RE: IDS 11 optimistic locking [2651] [Cross-posting only because we are discussing a v11 item under "classics".] This makes me wonder if this is a good way to handle those locks associated with active tables with serial values. Would this allow the engine to obtain the next serial value for a table even though someone may have performed an insert into the table but have not committed it yet due to the transaction(s) being "in progress"? .... or for those values in which you have a decimal field that you grab the last value of, increment by one and then perform your insert? Take care. Clifton M. Bean Informix DBA / AIX System Admin Currency Technics & Metrics Phone: (972) 812-1411 x244 -----Original Message----- From: classics-bounces@iiug.org [mailto:classics-bounces@iiug.org] On Behalf Of Mark Jamison Sent: Thursday, November 15, 2007 7:56 AM To: classics@iiug.org Subject: Re: IDS 11 optimistic locking [2650] Well IDS's optimistic locking is called DIRTY READ. In 11.10, we introduced what we refer to as OPTIMISTIC CONCURRENCY. Basically if your set the ONCONFIG variable USELASTCOMMITTED it means that IDS returns the last valid value for that row that has been committed. So for example, suppose you have session A begin work; update customer set fname = "FRED" where fname ="Fred"; And at the same time you have Session B; set isolation to committed read last committed; select fname from customer where fanme like 'F*'; In the above scenario, at session b would get the Value Fred from his select, even though session A is still holding a lock for the row holding the row or rows containing "Fred" for the column fname. Hope this Helps, Mark ----- Original Message ---- From: "Sharp, Kirk (USMS)" <Kirk.Sharp@usdoj.gov> To: classics@iiug.org Sent: Wednesday, November 14, 2007 3:40:29 PM Subject: IDS 11 optimistic locking [2637] Does anyone have any information on IDS 11's new 'optimistic locking' feature? **************************************************************************** *** Forum Note: Use "Reply" to post a response in the discussion forum. **************************************************************************** *** Forum Note: Use "Reply" to post a response in the discussion forum. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.

Hello, the new feature > In 11.10, we introduced what we refer to as OPTIMISTIC CONCURRENCY. > Basically if your set the ONCONFIG variable USELASTCOMMITTED > it means that IDS returns the last valid value for that row > that has been committed. could be helpful especially when porting applications from Oracle to Informix. Oracle returns COMMITTED DATA always and only, but that data may be 'outdated'. And that's still the difference: Oracle returns all the data for a special timestamp (change number), Informix the last committed. When you have long running SQLs/Transactions you may notice the difference. Regards, Andreas Kutsche > ------------------------------------------- SPAR Österreichische Warenhandels-AG Hauptzentrale A - 5015 Salzburg, Europastrasse 3 FN 34170 a Tel: +43 662 4470 24223 Mobile: +43 664 6259575 E-Mail: Andreas.KUTSCHE@spar.at Internet: http://www.spar.at Wichtiger Hinweis: Der Inhalt dieser E-Mail kann vertrauliche und rechtlich geschützte Informationen, insbesondere Betriebs- oder Geschäftsgeheimnisse, enthalten, zu deren Geheimhaltung der Empfänger verpflichtet ist. Die Informationen in dieser E-Mail sind ausschließlich für den Adressaten bestimmt. Sollten Sie die E-Mail irrtümlich erhalten haben so ersuchen wir Sie, die Nachricht von Ihrem System zu löschen und sich mit uns in Verbindung zu setzen. Über das Internet versandte E-Mails können leicht manipuliert oder unter fremdem Namen erstellt werden. Daher schließen wir die rechtliche Verbindlichkeit der in dieser Nachricht enthaltenen Informationen aus. 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The contents of the e-mail are only legally binding if they have been confirmed and signed by us in writing. If, in spite of our using Antivirus protection software, a virus may have penetrated your system through the sending of this e-mail, we do not accept liability for any damage that may possibly arise as a result of this. We trust that you appreciate our position. ------------------------------------------- -----Ursprüngliche Nachricht----- > Von: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] Im Auftrag von > Mark Jamison > Gesendet: Donnerstag, 15. November 2007 15:54 > An: ids@iiug.org > Betreff: Re: IDS 11 optimistic locking [10377] > > Hi Clifton, > > Keep in mind this is for reads only. > > If you have two writers: > > Session A > =========== > begin work; > update customer set fname="FRED" where fname="Fred"> > Session B > =========== > begin work; > update customer set fname="fred" where fname="Fred"> > They will still wait the same as they have always waited. > > Same goes for inserts. > > ----- Original Message ---- > From: Clifton Bean <cbean@ctm.com> > To: classics@iiug.org > Sent: Thursday, November 15, 2007 8:10:38 AM > Subject: RE: IDS 11 optimistic locking [2651] > > [Cross-posting only because we are discussing a v11 item under > "classics".] > > This makes me wonder if this is a good way to handle those locks > associated > with active tables with serial values. Would this allow the engine to > obtain the next serial value for a table even though someone may have > performed an insert into the table but have not committed it yet due to > the > transaction(s) being "in progress"? > > ..... or for those values in which you have a decimal field that you > grab the > last value of, increment by one and then perform your insert? > > Take care. > > Clifton M. Bean > Informix DBA / AIX System Admin > Currency Technics & Metrics > > Phone: (972) 812-1411 x244 > > -----Original Message----- > From: classics-bounces@iiug.org [mailto:classics-bounces@iiug.org] On > Behalf > Of Mark Jamison > Sent: Thursday, November 15, 2007 7:56 AM > To: classics@iiug.org > Subject: Re: IDS 11 optimistic locking [2650] > > Well > > IDS's optimistic locking is called DIRTY READ. > > In 11.10, we introduced what we refer to as OPTIMISTIC CONCURRENCY. > > Basically if your set the ONCONFIG variable USELASTCOMMITTED it means > that > IDS > returns the last valid value for that row that has been committed. > > So for example, suppose you have session A > > begin work; > update customer set fname = "FRED" where fname ="Fred";> > And at the same time you have Session B; > > set isolation to committed read last committed; > select fname from customer where fanme like 'F*';> > In the above scenario, at session b would get the Value > > Fred > > from his select, even though session A is still holding a lock for the > row > holding the row or rows containing "Fred" for the column fname. > > Hope this Helps, > > Mark > > ----- Original Message ---- > From: "Sharp, Kirk (USMS)" <Kirk.Sharp@usdoj.gov> > To: classics@iiug.org > Sent: Wednesday, November 14, 2007 3:40:29 PM > Subject: IDS 11 optimistic locking [2637] > > Does anyone have any information on IDS 11's new 'optimistic locking' > feature? > > ************************************************************************** > ** > *** > Forum Note: Use "Reply" to post a response in the discussion forum. > > ************************************************************************** > ** > *** > Forum Note: Use "Reply" to post a response in the discussion forum. > > > ************************************************************************** > ***** > Forum Note: Use "Reply" to post a response in the discussion forum. > > > ************************************************************************** > ***** > Forum Note: Use "Reply" to post a response in the discussion forum.