Re: Transaction logs and audit trails - quick overview required

In article <34c85f8c.72776308@news.demon.co.uk>, Ian Clark <ian@tubeway- army.demon.co.uk> writes >Hi All, > >I've just joined a company who are running an in-house developed >application written in Informix RDS and looking though the code I am >amazed to find that there is no transaction logging going in. >That means no BEGIN WORK, COMMIT WORK or ROLLBACK WORK. >Without these, in a multiuser enviroment I can only forsee problems >but by a freak of nature they seem to be getting along fine! > >To clarify the effect of transaction logging, can someone please >comment on the following: > >I understand that when starting a database with a transaction log >implemented, any database modiictions are logged to the database if >such statements are enclosed within BEGIN WORK...COMMIT WORK and that >ROLLBACK WORK ensures that the database is not updated. >If there are a number of users on the system and that the computer >could crash at any moment, would a simple ROLLFORWARD statement be all >that is needed to rectify the situation? Except that ROLLFORWARD needs a transaction log!! >Would a bcheck be adviseable before a ROLLFORWARD? Without a transaction log bcheck it the only answer after corruption. Of course with something like... INPUT value_a,value_b... END INPUT INSERT INTO a...value_a.. INSERT INTO b...value_b.. You really want either BOTH values in the database or NIETHER value. Of course, yo have no transactions so after doing a bcheck you could have value_a in the database and not value_b!! i.e. a logically inconsistent database. >Given that users could be at varying stages of update, would I be >right in syaing the ROLLFORWARD takes account of all the BEGIN WORK's >started by the users and that it would adjust the database as >necessary? > >Can someone please give a brief overview of audit trails and how >effective they are in monitoring the database. >What information is recorded in the trail for a table and can you >identify what user/program/process was responsible for a particular >update? >Sometimes users report that data is missing and a SELECT that returns >nothing confirms their suspisions but how are you to know what or who >was responsible? > >Any views/comments would be very much appreciated. > >Cheers, Ian. -- David Williams Maintainer of the Informix FAQ Primary site (Beta Version) http://www.smooth1.demon.co.uk Official site http://www.iiug.org/techinfo/faq/faq_top.html I see you standin', Standin' on your own, It's such a lonely place for you, For you to be If you need a shoulder, Or if you need a friend, I'll be here standing, Until the bitter end... So don't chastise me Or think I, I mean you harm... All I ever wanted Was for you To know that I care