A transaction is a unit of work consisting of one or
more SQL statements referencing one or more databases in a DBEnvironment.
Work done within a transaction can be committed (made permanent) or
undone (rolled back). A transaction is started with an implicit or
explicit BEGIN WORK statement and is either committed with COMMIT WORK
or rolled back with ROLLBACK WORK.
An IMAGE/SQL transaction is started by the first SQL statement that
results in a modification or repeatable read of an IMAGE/SQL table.
