Re: Change of Logging Status: Implications? -Reply
Peter Tashkoff wrote: > > Richard > I would have thought that the 4gl programs would > not be bothered by a move to transaction logging as > Informix treats each sql statement as a singleton > transaction anyway, so it should make no difference. > > I am not to sure about the esql/c. It depends on how > it is constructed. We have been running into > problems here with Cobol programs reading records > 'with lock'. Then re-writing them later. This works > fine under a non-logged database, but a database with > logging frees the log immediately after the read > (since it is not inside a transaction) with the result > that the cobol re-write is over to failure. We are > having to explicitly code transactions to work > around this. > If your c programs have some equivalent > expectation then you might run into problems like > this. > HTH > -- > -- > Peter Tashkoff > NZ Kiwifruit Project Consultant/DBA > Marketing Board. Standard Disclaimers apply > This posting may not be used by any commercial > organisation to vilify another. > > >>> Richard Spitz > <spitz@GANS2X.ana.med.uni-muenchen.de> > 1/August/1996 09:20pm >>> > Dear Informix Experts, > > I just discovered that a large and complex > application is running against a database with no > logging. Needless to say, the whole application is > written without transactions, which has been causing > numerous consistency problems in the database. The > developer has been catching most of these problems > by giving support to the users over the phone and > manually cleaning up after crashes, but this is now > getting out of hand. I had to convince her that using > transactions is mandatory, but I'm worried about the > implications of changing over the database to > logging mode. > It is a large application with thousands of lines of > code and using lots of cursors. I know that there are > several things you can only do inside a transaction > when the database is defined with logging, but I'm > not sure I know all of them. > > So I need info about the implications of changing a > database to logging mode. What problems are to be > expected in what parts of a program? I'll have to > assist the developer throughout the migration > process, without knowing too much about the > program itself and the database involved. If > I did know, I'd probably quit my job as DBA... These > problems have grown historically without me having > had much influence, so please refrain from > comments like "you should have known better". I > just have to save as much as possible. > > Database Engine is ONLINE 5.03, the application is > written using > ESQL/C 5.01 and 4GL 4.10. All of this is running in > client/server mode with both client and server > running on SNI RM400 machines under > SINIX 5.42B. > > Answers like "RTFM" are welcome as long as the > tell me which FM to R. > > Regards, Richard > -- > +----------------------------+-------------------------------------------+ > | Dr. Richard Spitz | INTERNET: > spitz@ana.med.uni-muenchen.de | > | EDV-Gruppe Anaesthesie | Tel : > +49-89-7095-3413 | > | Klinikum Grosshadern | FAX : > +49-89-7095-8886 | > | 81366 Munich, Germany | > | > +----------------------------+-------------------------------------------+ I tried to move a database from non-logged to logged and the problem I ran into was "lock table". This had to be done inside a transaction, e.g. after a "begin work". This would have been do able, but the way the program was written, processing a table at a time up to 6 tables, would have created a very large transaction which was unacceptable.