Re: longops vs sql

Brian Peasland wrote:
> > Wouldn't that also be based upon how many physical reads were actually
> > required? Say if you had a huge buffer cache and rarely had to go to
> > disk for your data, that value could be quite smaller then, correct?
>
> If the data was cached, then it is a logical read. No physical read
> required.
>
> > I have a few snap shots from our system, so I looked at our Load
> > Profile, it lists:
> >
> > Load Profile
> > ~~~~~~~~~~~~ Per Second Per
> > Transaction
> > ---------------
> > ---------------
> > Redo size: 153,299.18
> > 3,927.45
> > Logical reads: 16,661.37
> > 426.86
> > Block changes: 540.73
> > 13.85
> > Physical reads: 1,752.49
> > 44.90
> > Physical writes: 152.31
> > 3.90
> >
> > So from this I should probably assume that at that point in time we
> > were acheiving 1,752 I/O / sec? Would I add the writes into that to see
> > the total I/O / sec?
>
> Your Oracle database, during this snapshot interval, was performing
> 1752.49+152.31= 1,904.80 I/O requests per second, on average. During
> that interval, you could have had more I/O requests in one second, or
> less. This is just an average per second on that snapshot interval.
> Total I/O operations is the sum of physical reads and writes.
>
> The unit of I/O is the database block. Your OS often has a different
> block size so it could have been performing even more I/O operations per
> second. For instance, if your database block is 8KB and your OS's
> filesystem has a block size of 2KB, then one database I/O operation gets
> translated to 4 2KB I/O operations.
>
> HTH,
> Brian
>
>
>
> --
> ===================================================================
>
> Brian Peasland
> dba_at_nospam.peasland.net
> http://www.peasland.net
>
> Remove the "nospam." from the email address to email me.
>
>
> "I can give it to you cheap, quick, and good.
> Now pick two out of the three" - Unknown

very good stuff, thanks so much! Received on Thu Sep 07 2006 - 20:41:29 CDT