Re: DB Block Size-Your Opinions

general rule - from everything i've read lately, hear at users group meetings and in oracle classes just about any database being created today should have at least an 8k block size. the 2k default that oracle ships with was appropriate 10 years ago, but not today. it is possible that a database with small transactions and few full table scans might run just as good with a 2k block size, but there are not many databases like this. our app is a customer billing system, and we bumped the block size to 8k a while back. noticed the same cache hit ratio, but much faster reporting performance. now we try to create all databases at 8k if possible. even if the rows are all smaller than 2k or 4k, any reports, multi-line blocks, or queries of more than a single row will benefit by the reduction of the number of physical reads. more importantly, most current disk subsystems are reading more than just 2k at a time. so it is important to match up the block size and multiblock read parameters so they match what your hardware is doing.

i'm sure there are many DBAs out there capable of explaining this better than i just tried to, but i hope this helps a little.

sam

Chakravarthy KM Nalamotu <kittu_at_Hawaii.Edu> wrote in message news:7h6tlk$g6n_at_news.Hawaii.Edu...
> I came across a general recommendation to use 8K blocks
> for databases that are large. My Definition of large
> is anything greater than 20 GB.
> Wouldn't it be better to use 4K or even 2K blocks if I am
> sure that a single row of any table in the database will
> not be more than 4K or 2K?
> This way I am not briniging in all the unnecessary rows
> into the cache. Furthermore, cache has larger number
> of smaller relevant data blocks.
> Your thoughts on this topic are greatly appreciated.
>
> Thank you,
> Kittu.
Received on Mon May 10 1999 - 21:06:32 CDT