Re: Low Hit Ratio

If you have available real memory, increasing cache size may give you some relief. But watch out, because like Jim says your reports may be using disparate data and are flushing the cache. If this is the case, then you would need a very large cache to significantly lower the cache hit ratio. And a large cache may actually reduce performance if real memory is needed more for other purposes.

Slicing the pie up differently may not help. You may just need a bigger pie.

"Jim Kennedy" <kennedy-down_with_spammers_at_attbi.com> wrote in message news:XIeT9.622713$%m4.201217_at_rwcrnsc52.ops.asp.att.net...
> 1. You are asking for trouble in noarchive log mode unless it is easy to
> restore the data from some other source.
> 2. A high buffer hit ratio is not neccessarily meaningful. They are
 running
> a bunch of reports, the data might never have been asked for before, so of
> course you are going to get cache misses. What performance problem are
 you
> experiencing? Work on that not increasing the cache hit ratio.
> Jim
>
> --
> Replace part of the email address: kennedy-down_with_spammers_at_attbi.com
> with family. Remove the negative part, keep the minus sign. You can
 figure
> it out.
> "Mahesh Hardikar" <hardikarm_at_yahoo.com> wrote in message
> news:4a1c57c2.0301090023.14bbdfeb_at_posting.google.com...
> > Hi ,
> >
> > Oracle Version 8.1.7 on HP-UX 11 with 4GB RAM & 3 CPU's (540MHz).
> > Machine Hosts Oracle Apps 11i & Database Server as well.
> >
> > Current settinngs in init.ora are :
> >
> > DB_BLOCK_BUFFERS 80000
> > DB_BLOCK_SIZE 8192
> > Shared_pool_size 382 MB
> > Log_Buffer_size 10MB
> > processes 750
> > open cursors 900
> > session cached cursors 900
> > log_checkpoint_interval 100000
> > sort_area_size 1024000
> > db_writer_processes 3
> > dbwr_io_slaves 3
> > timed_statistics true
> > cursor_space_for_time TRUE
> >
> > Current database size is around 48GB & database is in NOARCHIVELOG
> > mode.
> >
> > We are experiencing low cache hit ratio like 60% in peak hours i.e.
> > when users fire lot many reports.
> >
> > I wish to know if I have some room to increase DB_BLOCK_BUFFERS. 625
> > MB SGA for 48GB DB seems low . But I want to know till how much can i
> > raise it ? Since no of processes are ard 750, how much memory do they
> > take in all ?
> >
> > Any advise on this is kindly appreciated ....
> >
> > Regards ,
> > Mahesh Hardikar
>
>
Received on Thu Jan 09 2003 - 15:25:02 CET