What MB/s is pulled from your buffer cache?

From: Rich Jesse <rjoralist2_at_society.servebeer.com>
Date: Tue, 12 Feb 2013 14:22:35 -0600 (CST)
Message-ID: <72f8904b5f2e8f3c8d9ff87eb0082dbc.squirrel_at_society.servebeer.com>

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.

TIA! Rich

p.s. The extra columns are for me to verify my calculations -- feel free to scrutinize with feedback!

--
http://www.freelists.org/webpage/oracle-l

Received on Tue Feb 12 2013 - 21:22:35 CET