Re: What MB/s is pulled from your buffer cache?

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_at_society.servebeer.com> To: <oracle-l_at_freelists.org> 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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