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Home -> Community -> Mailing Lists -> Oracle-L -> Re: DB Block Buffers - Too Much ???
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Deepak Sharma wrote:
> No, the system has been running with activity for
> quite a while. I also checked 'vmstat 3 5' a few times
> and this is the o/p (showing slight swapping looking
> at pin and pout):
>
> procs memory pages
> intr cpu
> r w u act free wire fault cow zero react pin
> pout in sy cs us sy id
> 7230 29 218K 2832 34K 261M 60M 60M 122K 58M
> 6824 637 1K 1K 13 6 82
> 6230 30 220K 964 34K 736 11 683 0 13
> 0 67 5K 910 88 12 0
> 6230 30 221K 193 34K 196 0 196 15 0
> 10 385 6K 1K 82 18 0
> 7230 29 221K 128 34K 196 0 196 0 0
> 0 216 3K 1K 83 17 0
> 7230 29 221K 128 34K 197 0 196 0 0
> 0 549 4K 2K 77 21 2
>
> Also, I used 'swapon -s' and got this :
>
> Total swap allocation:
> Allocated space: 768771 pages (6006MB)
> In-use space: 28802 pages ( 3%)
> Available space: 739969 pages ( 96%)
>
> showing 3% being used for swapping.
>
> Somebody pls correct me interpreting this if i'm
> wrong, 'cause I'm not much of a Unix SA.
>
> -- Deepak
>
> --- "Weaver, Walt" <wweaver_at_rightnowtech.com> wrote:
> > Just out of curiousity, did you measure hit ratio
> > soon after re-starting the
> > database? Wouldn't the hit ratio be misleadingly low
> > for a while, since
> > Oracle was probably busy reading disk and loading
> > stuff into the buffers?
> >
> > Other than that, I suppose you could monitor vmstat
> > or some other utility to
> > see if excessive memory swapping is going on.
> >
> > --Walt Weaver
> > Bozeman, Montana, USA
> >
> > -----Original Message-----
> > Sent: Wednesday, June 21, 2000 11:26 AM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Recently on one of our test systems the Buffer Cache
> > Hit Ratio was showing 80%. I increased
> > db_block_buffers from 6000 to 16000, and the after
> > that the hit ratio has dropped to 55%. It seemed
> > strange to me that increasing db_block_buffers
> > should
> > actually decrease performance, until I read Oracle
> > tuning tips from Richard Niemiec, where he mentions
> > too much db_block_buffers is not good too, as it may
> > lead to swapping. My question is how do you
> > determine
> > whether the buffers are too low or too high ?
> >
> > SQL> select state, count(*) from x$bh group by
> > state;
> >
> > STATE COUNT(*)
> > ---------- ----------
> > 1 13047
> > 3 2953
> >
> > Does state = '1' mean this memory is not being used
> > and if so, should I decrease the buffers ?
> >
> > -- Deepak
> >
> > =====
> > Oracle DBA,
> > Minneapolis, MN
> > USA
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Send instant messages with Yahoo! Messenger.
> > http://im.yahoo.com/
> > --
> > Author: Deepak Sharma
> > INET: sharmakdeep_at_yahoo.com
> >
> > Fat City Network Services -- (858) 538-5051 FAX:
> > (858) 538-5051
> > San Diego, California -- Public Internet
> > access / Mailing Lists
> >
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> > --
> > Author: Weaver, Walt
> > INET: wweaver_at_rightnowtech.com
> >
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> =====
> Oracle DBA,
> Minneapolis, MN
> USA
>
> __________________________________________________
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> Send instant messages with Yahoo! Messenger.
> http://im.yahoo.com/
> --
> Author: Deepak Sharma
> INET: sharmakdeep_at_yahoo.com
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
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Deepak:
Please look at the meaning of swap options.
Used here means allocated or reserved.
-s Print summary information about total swap
space usage and availability:
allocated The total amount of swap space
(in 1024-byte blocks)
currently allocated for use as
backing store.
reserved The total amount of swap space
(in 1024-bytes blocks) not
currently allocated, but
claimed by memory mappings for
possible future use.
used The total amount of swap space
(in 1024-byte blocks) that is
either allocated or reserved.
available The total swap space (in
1024-byte blocks) that is
currently available for future
reservation and allocation.
These numbers include swap space from all
configured swap areas as listed by the -l
option, as well swap space in the form of
physical memory.
..varad
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Received on Wed Jun 21 2000 - 17:12:54 CDT
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