Re: buffered logging - sybase vs. informix

johnl@informix.com (Jonathan Leffler) wrote: >>From: john b <jointprd@crl.com> >>Date: Mon, 18 Mar 1996 13:22:06 -0800 >>X-Informix-List-Id: <news.22233> >> >>First some background info - I'm a Sybase DBA with a potential INFORMIX >>project coming up. So... I'm reading my INFORMIX DBA SURVIVAL Guide and >>I come across the section on buffered logging. I think this is pretty >>cool stuff - Sybase doesn't have this. At the same time I'm thinking of >>potential uses for buffered logging. The only thing that really comes to >>mind is static info. like a DSS database. So my question are: >> >>1) how many folks are actually using buffered logging? > I've used it in the past, mainly on databases with a low update volume > where the update activity was not mission critical (read-mainly databases). >>2) has anyone experienced loss of data? > Yes, but not often. It requires the machine or OnLine to crash out of > control, and the logs not to have been flushed to disk since the last > commit. This is (should be) relatively rare, not least because the > hardware is pretty reliable these days. > But by definition, if you are using buffered databases, this data loss > is not significant. If it is significant, you should not use buffered > databases. >>3) can you actually force the buffers to disk via a "checkpoint"? > Of course. Also by using SET LOG. But, as stated previously, if your > database is buffered, you have concluded that the risk of lost data is > not significant. >>[...Request for Sybase-Informix comparison omitted...] >Yours, >Jonathan Leffler (johnl@informix.com) #include <disclaimer.h> Using buffered or unbuffered logging is performance verses lose of data. The most you will ever lose with buffered logging is what happened since the last checkpoint. The question to use it or not is does it increase performance enough to risk the lose of a checkpoints worth of work if the engine crashes. The other thing to keep in mind is how often does the engine crash or the os crash. If you have taken the pains to set up your hardware with no single point of failure and mirroring everything on disk for a high availablity system then you probably do not want buffered logging. However if this is not the case the lose due to buffered logging is not near the risk of the lose due to other hardware factors. As far as informix vs. sybase the biggest difference is row level locking and intelligent fragmentation informix offers. Both offer most of the other features . The way the products are sold is also a big difference. Cost could be the biggest difference when you price all the pieces you need for an application. -- Tolly Brumbelow, Informix DBA email:tolly.brumbelow@bridge.bellsouth.com