Re: Physical block reads difference

From: Jayaraman Ashok <ashok_jayaraman_at_yahoo.com>
Date: 26 Sep 2002 22:15:34 -0700
Message-ID: <7ca2852.0209262115.75fa9ae5@posting.google.com>

Hi
SQL> select name,value from v$sysstat where name = 'physical reads';

NAME VALUE

---

---

physical reads 5406826159

SQL> select sum(phyrds),sum(phyblkrd) from v$filestat;

SUM(PHYRDS) SUM(PHYBLKRD)
----------- -------------
 1242069868 5317548754

SQL> The assumption that physical reads of v$sysstat is always less tha or equal to physical block reads from v$filestat is wrong. How torelate the two values between v$sysstat and v$filestat ? Which is to be taken into account and why? Hope somebody can explain in detail about these......

Cheers,
Ashok
oratune_at_msn.com (David Fitzjarrell) wrote in message news:<32d39fb1.0209260955.2d7185a2_at_posting.google.com>...
> Had you looked further into the view you would have also seen PHYRDS,
> reporting physical reads, along with PHYBLKRDS, and you would have
> noticed the difference between the values there. As such, PHYBLKRDS
> is NOT the same as PHYRDS.
>
> Since a single physical read may span more than one physical block,
> just as a physical write may write multiple blocks in a single
> request, it's not surprising that PHYBLKRDS exceeds the value for
> PHYRDS.
>
> David Fitzjarrell
>
> ashok_jayaraman_at_yahoo.com (Jayaraman Ashok) wrote in message news:<7ca2852.0209260221.37be8227_at_posting.google.com>...
> > Hi
> > I queried the v$sysstat for getting the 'physical reads' on the
> > database. I believe this is the number of physical block reads. Now
> > querying the sum(phyblkrds) in v$filestat, shouldn't the value be the
> > same? I think both the statsistics are one and the same. But then why
> > the difference? Kindly explain.
> >
> > Cheers,
> > Ashok
Received on Fri Sep 27 2002 - 00:15:34 CDT