Re: Background Processes and I/O

From: Michael J. Moore <NOhicamelSPAM_at_comcast.net>
Date: Sun, 21 Dec 2003 04:06:01 GMT
Message-ID: <J_8Fb.103585$8y1.319067@attbi_s52>

"Ana C. Dent" <anacedent_at_hotmail.com> wrote in message news:8t8Fb.32649$BQ5.21787_at_fed1read03...
> Michael J. Moore wrote:
> > Okay, but why would CKPT be any more true than SMON? Does not SMON also
> > perform I/O?
> >
> >
> > "Ana C. Dent" <anacedent_at_hotmail.com> wrote in message
> > news:ZK6Fb.32237$BQ5.9627_at_fed1read03...
> >
> >>Michael J. Moore wrote:
> >>
> >>>From 9i Self Test ...
> >>>
> >>>Which 4 background processes perform I/O? (Choose 4)
> >>>
> >>>* DBWn
> >>>* ARCn
> >>>* PMON
> >>>* SMON
> >>>* CKPT
> >>>* LGWR
> >>>-----------------
> >>>I thought they all did, except CKPT which tells DBWn to do it, and PMON
> >>>which only works with memory structures.
> >>>
> >>>Their answer was all except SMON and PMON. In reality, none of them do
> >
> > I/O
> >
> >>>because they call OS library routines to do the actual I/O. This is
why
> >
> > I
> >
> >>>don't have a chance in hell of passing this test, because too many
> >
> > answers
> >
> >>>depend on how you consider the question. ;-)
> >>>
> >>>Any comments?
> >>
> >>I agree with "their" answer.
> >>Which process writes to the control files?

>
>

> Top posting is rude!

>


> DBW - does I/O to datafiles

> ARC - Does I/O when archiving redo logfiles

> CKPT- Updates control files.
> LGWR- Writes redo logfiles.
> To which file(s) does SMON read & write?
>

Sorry, I didn't know that top posting is rude.

SMON performs instance recovery, so it must read from redo logs. The manuals I have read are not clear on how SMON does this, but if it does read, then that counts as I/O, right? SMON also cleans up temporary segments anc coalesces free extents. Can it do this without performing I/O? Received on Sat Dec 20 2003 - 22:06:01 CST