this looks to me as if either the transaction was committed/rolled back unconsciously or a timeout happened (more likely). OpenAccess will close long running transactions on the server side in order to
lessen the burden on the server, and this could be a symptom of such a timeout condition. Please make sure that you do not use possible blocking calls when iterating over a result set; everything where the user is involved is 'dangerous' as he might have gone for a coffee break while the transaction is in progress. In order to avoid such situations consider transferring the query result to a list before presenting the results to the user.
You can also set the 'Active connection timeout (secs)' from the backend configuration dialog / Connection to a value greater than 120 seconds.
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