"SELECT ... FOR UPDATE"

Normally, when a dynaset is created, rows are not locked in the database until Edit is invoked. If this is not desirable, you might include the FOR UPDATE construct in the SQL SELECT statement. Unfortunately, the FOR UPDATE construct undermines normal dynaset operations, so Oracle does not recommend its use.

Dynasets created with FOR UPDATE are handled correctly in most cases by scanning the SQL statement for the FOR UPDATE construct (This is necessary because the Oracle database functions do not distinguish between SELECT and SELECT FOR UPDATE SQL statements.) It is possible that some exotic FOR UPDATE SQL statement will be treated as "not FOR UPDATE"—meaning that rows are not locked during the lifetime of the dynaset. If the FOR UPDATE is not recognized, rows are locked only during an Edit/Update sequence. However, during the Edit/Update sequence, the row is verified as unchanged before the Edit is permitted.

The use of FOR UPDATE on dynasets requires that a session level transaction be in progress at the time the dynaset is created. Further, before the session can be committed or rolled back, all objects which reference the dynaset must be set to "Nothing" or an error is returned. In the case of a data control, change the record source and Refresh the data control or Recordset.

Note that if an error results and the application terminates, uncommitted data is rolled back, including pending FOR UPDATE dynasets.