Programming Guide - Actian

How You Can Use Data Entry Error HandlersRestrictions on Data Entry Error HandlersA data entry error handler is subject to the following restrictions that areimposed on the handler and on any procedures or methods it calls:• Handlers cannot invoke a frame; the callframe, gotoframe, and openframestatements are all illegal.• Handlers cannot wait for user events or database events, but they canissue database queries and do file I/O.• The OpenROAD Debugger does not stop at breakpoints or for any othercondition during the execution of the handler.Statements that usually cause display of a pop-up frame (when executedoutside a data entry error handler), such as the message statement andthe ConfirmPopup method, are written to the trace window and thew4gl.log file.Except for message statements, such statements cause the entireOpenROAD process to wait for a response, even if there are other threadsthat could run.A handler can be in a thread different from that of the frame that encounteredthe error, even if the handler is a local procedure.Note: The error handlers described in this section do not apply to databaseerrors. For more information about handling database errors, see Working witha Database (see page 147).Data Entry Error Handling 315