Snapshot problem: Update in cursor

Hi!

We've spotted a problem while migrating our application from Informix Online to Oracle. Scenario is as follows:

• Starting transaction
• Opening a cursor which will get 5 rows (for example), these may be row 1, which contains a 10, row 2, containing a 20 and so on up to row 5 which contains a 50.
• After fetching 2 rows, one after the other, we perform a select of row 4, modify its value from 40 to 42 and write it back using update - _no_ commit! (so we're not talking about updates across commit; the modified value is neither part of the where clause nor an index column)
• Next fetch ...
• Sooner or later row 4 is fetched by the cursor and, surprise, surprise, it contains the initial value 40 instead of the lately written 42!

This is not the behavior we've expected. And it doesn't meet the way Informix Online reacts - it gives the IMO "correct" value 42.

Oracle support says everything's fine. This is their understanding of consistency (long explanation of System Change Numbers and Fetches Across Commit snipped - because there are no commits!!!).

Our understanding of consistency is a different one - the one which Informix shares (and the one, which complies common sense, we suppose). ;-)

Do you have similar experiences, problems or maybe a clue or trick to solve this problem? Maybe it's possible to refresh the snapshot which was taken at the start of the cursor to get the changes I've made (but not those, other transactions have made)? Any suggestions?

Thnx in advance.

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Sincerely, Dirk Straka                    Due to email spammers, reply
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Dr. Brunthaler GmbH, Berlin               change NOSPAM to Insel. Thnx