Re: What MB/s is pulled from your buffer cache?
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 13 Feb 2013 17:14:58 -0000
Rich,
100MB/s at 8KB per block would only be 12,000 logical I/Os per second.
I don't know how small, or quiet, your database might be, but pulling up a
couple of statspack and AWR report I have on my machine I've got several
show their load profile in the 60,000 to 120,000 LIOs per sec, and a busy
one running at 320,000 LIOs per se.
12,800 doesn't sound dramatic.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com/all-postings
Author: Oracle Core (Apress 2011)
http://www.apress.com/9781430239543
----- Original Message -----
From: "Rich Jesse" <rjoralist2@xxxxxxxxxxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Tuesday, February 12, 2013 8:22 PM
Subject: What MB/s is pulled from your buffer cache?
| Howdy,
|
| In our 11.2.0.3 production DB, I was looking at v$sysstat, and happened
to
| order the view by VALUE DESC for kicks. The highest number is for the
| 'logical read bytes from cache' stat and is currently over 500TB. That
| seems abnormally large for less than 2 months of our ~800GB DB, so I
thought
| I'd see what that boils down to in MB/s:
|
| SELECT
| vs.value cache_read_bytes,
| vi.startup_time,
| ROUND(SYSDATE-vi.startup_time,2) uptime_days,
| (SYSDATE-vi.startup_time)*24*60*60 uptime_seconds,
| ROUND(vs.value / ((SYSDATE-vi.startup_time)*24*60*60)) bytes_per_sec
| FROM v$instance vi, v$sysstat vs
| WHERE vs.name = 'logical read bytes from cache';
|
| It's over 100MB/s, which my knee jerk (emphasis on the latter) tells me
that
| this seems abnormally high for our li'l DB.
|
| I'm curious to see how that number compares to other installations, if
folks
| are willing.
|
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