setjmp()/longjmp() and RDS

To all IPC and Trigger-Fans! Our Configuration and installation-order: SCO 3.2.4 Informix SQL 4.11.UC1 Informix RDS 4.11.UC1 Informix ID 4.11.UC1 Informix Online 5.01.UD2 Please have a look at the following scenario: 1. There is a table called `lager' representing the real-world stockroom (german Lager). In this stockroom is beside others the article `screw' and the actual amount. 2. There is a module which allows a user to create a delivery note (german Lieferschein). 3. The user X now wants to sell and deliver some amount of screws. So we select and display the actual amount from the table `lager' that the user can decide wether he's able to sell the whole amount or not. 4. While the user X has the information on the screen and the purchaser at the telefon, he decides that the amount of this article the purchaser wants to buy is enough. 5. While speaking with the purchaser, user Y unfortunately sold the whole amount of the screws. 6. At the moment user Y's process updates the table `lager', we want user X to inform about the change. We want to tell him immediately, that the information on the screen is no longer valid. And now the big question is: WHAT IS THE MOST-EFFECTIVE AND EASIEST-TO-IMPLEMENT STRATEGY TO IMPLEMENT THIS `Real-Time'-Database-Applikation with RDS? There are several starting points, we think: 1. We heard and read something about `triggers', which are said to be related to tables. But all we found in the whole documention of our products was a short hint in the release notes that there should exist two commands CREATE TRIGGER and DROP TRIGGER, but nothing (in words: NOTHING) about thesyntax of these statements. The question here is: Where can we get information about the syntax and usage of the triggers-mechanism????? 2. We have some experience with the C-function-pair setjmp()/longjmp() and so we think it should be possible to implement a complex mechanism like the following: a) With a C-routine holding a sigaction()- and a setjmp()-call we activate the listening to a userDefined signal before selecting and displaying the `lager'-information. b) On receive of the userDefined signal, the other with sigaction() specified C-routine executes the longjmp()-call so that a error-statement could inform the user about a change of the amount of screws before selecting and displaying this information again. c) After every update of the table `lager', there should be a call to a C-routine which sends the userDefined signal to every database-process (via a call to the kill()-function after examining the process-table). d) Upon leaving the delivery note - module, the listening to the userDefined signal must be deactivated due to another sigaction()-call. The questions here are: 1. Could the implementation be done without setjmp()/longjmp()??? 2. DO THESE C-routines AND THE RDS-Interpreter work together in the outlined way???? or is it completely impossible for both to comunicate in this asynchronous manner???? So long, Richard -- Richard Bahcic Email: rb@argon.in-ulm.de