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Step 3. AutoCommit Mode. Work in the context of two transactions for avoiding DEADLOCK.

pFIBDataSet allows to commit the made changes automatically if you set AutoCommit to True. Now after calling the Post method, pFIBDataSet1 will automatically call pFIBTransaction1.CommitRetaining, saving the changes without closing the query. Such approach decreases the probability of Deadlock, which is possible in the presence of long unclosed transactions, in the context of which were made data changes.

But FIBPlus gives another capability, which practically reduces the probability of Deadlock to zero. TpFIBDataSet can work in the context of two transactions, a long one in the context of which the data are only read and a short one, in the context of which there executed all modifying queries.

Let's rename pFIBTransaction1 into ReadTransaction and add another component called WriteTransaction. After this we set UpdateTransaction of pFIBDataSet1 in WriteTransaction. Thus pFIBDataSet1 is connected to both components of TpFIBTransaction at once:

Figure 13.

Now after calling the Post method pFIBDataSet1 will call Commit of WriteTransaction. But taking into account the fact that the data are read in the context of a different transaction (ReadTransaction), it will not cause close of pFIBDataSet1. So using FIBPlus we have a real AutoCommit mode, which decreases the possibility of Deadlock and does not prevent us from seeing all actual record values. You might know that while using BDE in the AutoCommit mode you cannot get real record values without reopening the query.

See the full example code.

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Preview text: Devrace FIBPlus: Peculiarities of master-detail mechanism in the course of work with InterBase. Step 3.
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We are a small software company with thousands of customers delivering comany wide systems including accounting, logistics, e-commerce, POS, sales etc etc. Several years ago, when we were still a very small company, we used Delphi 3 and Paradox combined with BDE. As our system (and customer base) grew I decided to switch to Delphi 5 and Interbase. Being a huge improvement over Delphi 3 and Paradox, I encountered numerous problems with IBX: memory leaks, performance issues and other problems. Borland was not to be bothered: IBX was provided "as is" and no support was avaliable. 
Not being very eager to use third party components with Delphi at first, I decided to give FIBPlus a try. At once all problems where gone: no more memory leaks and  performance was very consistent. 
But the real advantage of switching to FIBPlus came with the upgrade to D2005: after upgrading there were some problems with the new FIBPlus version. After emailing the problem I received an update within an hour! And this was at 11 pm! A few other (smaller) errors where handled in the same way. 
Our motto is: software is as good as its support. And support of Devrace is just great!
Just a little indication of our FIBPlus use: all our software runs 100% on FIBPlus. Our customers have a total of aprox. 4.800 Firebird databases in production, with a combined size of over 130TB and over 80 million transactions a day. Every
day. And FIBPlus has not failed a single transaction. Not once. There is, however, one (minor) drawback in using FIBPlus: while debugging an application which uses and invalid SQL instruction, de Delphi Debugger returns to the FIBPlus code instead of to our calling code (where the actual error comes from), thereby complicating de debug proces a little. But that is a very small price to pay for a otherwise brilliant third party solution! >>

Bas Jordans JorSoft Ltd
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