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Re: Checkpoint duration

From: <timur.gokce_at_gmail.com>
Date: 26 Nov 2006 23:20:35 -0800
Message-ID: <1164612035.411508.66130@l39g2000cwd.googlegroups.com>


During a checkpoint the following occurs:

i ) If I increase or decrease # of datafiles (from 10 to 5000 or vise-versa) in my database ,Will this effect the time spent to checkpoint ?
ii) By considering the time elapsed between "checkpoint started" and "checkpoint completed" logs in the alert.log. For which task above does it spend much time ?

On Nov 27, 2:28 am, "hpuxrac" <johnbhur..._at_sbcglobal.net> wrote:
> timur.go..._at_gmail.com wrote:
> > Checkpoint process updates the file headers of the data files and
> > flushes the dirty buffers in cache to data files.
>
> > i) Is there any propotional relation between "number of datafiles" and
> > time spent to perform a checkpoint ?Often the time spent updating the file header is minor compared to
> other checkpoint activity. Logically yes there is a relationship.
>
> The actual times taken will vary considerably depending on your io
> configurations and whether you support async io etc.
>
> > ii) Is the majority of the time spent to checkpoint caused by "header
> > update"(LGWR) or "flushing dirty buffers"(DBWR) ?In general it depends on the system and varies widely. What do you
> mean by header update and LGWR?
>
> Log writer also goes first. If there are many dirty buffers in your
> buffer caches then the time taken to do this flushing will probably
> dwarf the amount of time required to update the file headers.
Received on Mon Nov 27 2006 - 01:20:35 CST

Original text of this message

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