James Lampert wrote:
The easiest way to veto a change from a "before" trigger is what?
Cause the trigger program to fail with a fatal error?
I know I have an example of a trigger program that vetoes everything
unconditionally (I wrote one to exercise QuestView's trigger veto
detection feature some years ago), but I can't remember what it did,
or where I put it.

Optionally send a diagnostic message, for example to the requester of the I/O, and then... Send an Escape message to the program previous to the trigger program; i.e. to the DB I/O program. When that DB I/O program receives the escape message, that will effect termination of the trigger and manifest that as an I/O error to the program that requested the I/O. Due to implementation details, that escape message will become irretrievable; it will not be visible, neither in a trace nor joblog, and why the diag message may be valuable if the I/O requester needs some information about why the I/O was prevented\vetoed.

Regards, Chuck

This thread ...

Replies:

Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2019 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].