> trans.Isolation := tiConcurrency;

Try tiCommitted

Read the page Transaction Isolation in the help for details of why.
tiConcurrency is the dafault simply because BDE does it wrong!

> So I don't need to explicitly call starttransaction for this? What
> about commit? Isn't the best approach to explicitly specify the
> behavior?

The StartTransaction is included automatically. You only need to
included it if you want to disable 'AutoCommit' for a particular set of
actions, and then 'AutoCommit' is restored when a Commit or Rollback are
used. As you have AutoCommit off, any post action will automatically
StartTransaction, and so you only need to Commit when finished.

--
Lester Caine
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L.S.Caine Electronic Services