Re: Correlation? init.ora: db_files and controlfile: maxdatafiles

"Sean Fitzgerald" <sfitzgerald_at_centurytel.net> wrote in message news:FHtu7.8568$tE2.4236012_at_feed.centurytel.net...
>
> "Sybrand Bakker" <postbus_at_sybrandb.demon.nl> wrote in message
> news:trk993kejc0jd4_at_news.demon.nl...
> >
> > "Johannes Bavendiek" <JohannesBavendiek_at_gmx.de> wrote in message
> > news:df6af3e.0110020614.2e3ed483_at_posting.google.com...
> > > Question for Oracle 8.0.4 and Oracle 8.1.7.
> > >
> > > We have a large DB with 238 files, and it is still growing.
> > > The init.ora parameter DB_FILES is set to 254.
> > > It is easy to increase it (set to 1024 and restart DB).
> > >
> > > But in the controlfiles there is a parameter MAXDATAFILES, also set to
> > 254.
> > > Do I have to increase this also?
> > > And how?
> > >
> > > What is the correlation between db_files and MAXDATAFILES?
> > >
> > > cu
> > > Johannes
> >
> >
> > Max_data_files is the *static* limit which was used in creating the
> > controlfiles.
> > This means you won't be able to increase db_files beyond max_data_files.
> > Normally you would need to recreate the database.
> > However I think that using more than 200 datafiles is *very undesirable*
> and
> > if I would have to consult at your site I would address this issue
> > *immediately*
> >
> > Hth,
> >
> > Sybrand Bakker, Senior Oracle DBA
> >
>
> In 8i maxdatafiles is not static. It will automatically grow up to a
> maximum of 65536 on unix systems. No controlfile recreation necessary.
You
> can keep increasing db_files in the init.ora. However, if you are
> constantly adding files to the database you should make sure you are
sizing
> them large enough (ie, don't create many, small datafiles where one or two
> big datafiles will do).

Given that the smallest unit of backup and recovery is a datafile, I can't agree that a few big files are necessarily worse than many small ones. Lots of files equals longer checkpoints, 'tis true. But lots of small files also means finer granularity of backup and recovery, and (suitably spread out amongst multiple devices) better general running performance in the absence of checkpoints.

As ever, there's a balance to be struck between checkpoint time and recovery time, but just decrying small files (ie, around 500Mb - 1Gb) per se seems perverse.

Regards
HJR
>
>
Received on Wed Oct 03 2001 - 03:57:39 CDT