Re: checkpoint
rkusenet wrote: > "Franklin Tang" <franklin@macauslot.com> wrote : > >>Dear all, >> what is the impact to increase the CKPTINTVL value. Any side-effect??? >>If my system crash, do I lose more data because the buffer doesnt get fushed >>by the checkpoint action??? I know the LRUs will fush when it reachs the >>LRU_MAX_DIRTY. Anyone can give me more clear explaination. In general, increasing the checkpoint interval will increase the checkpoint duration. Whilst the writes performed at checkpoint time are the most efficient, they tend to cause performance issues for users. Certainly the LRU_???_DIRTY parameters can help reduce the work done at checkpoint time, but they do not represent a recovery point. > It is one of the misconception that when LRU cleaners flush dirty pages, > it gurantees that the changed data will be there after a system crash. That > is wrong. It will be there, but may not represent a consistent state. > So my advice, if your database is logged , you can keep as high a value of CKPTINTVL as > you feel comfortable. I would not mind keeping an interval of even 1 hour. You would > benefit from LRU writes as opposed to chunk writes which blocks the system. > The only downside is that it will take longer to recover from a crash as it has to apply > all changes since last checkpoint. But I have seen that fast recovery is very fast. > I can live with that. You will of course place a large burden on logical log space. To my mind, ANY recovery time is an increase in downtime, which can be minimised in a well tuned system. Personally, I would be worried to see a checkpoint frequency more than 5 minutes on an OLTP production system. Cheers, -- Mark. +----------------------------------------------------------+-----------+ | Mark D. Stock mailto:mdstock@MydasSolutions.com |//////// /| | Mydas Solutions Ltd http://MydasSolutions.com |///// / //| | +-----------------------------------+//// / ///| | |We value your comments, which have |/// / ////| | |been recorded and automatically |// / /////| | |emailed back to us for our records.|/ ////////| +----------------------+-----------------------------------+-----------+