If they are below the high water mark, they'd be included in your level 0
backup, but if they *remain* empty, subsequent incrementals will skip them.
Regards
HJR
"Ted Chyn" <tedchyn_at_yahoo.com> wrote in message
news:44a19320.0108300953.46d35b97_at_posting.google.com...
> howard, thnx for the reply. If I have a table with 500mb under hwm
> 500mb will be backup by rman even when most records were deleted ?
>
> thnx again.
>
>
> "Howard J. Rogers" <howardjr_at_www.com> wrote in message
news:<3b8e22a3$1_at_news.iprimus.com.au>...
> > The Backup and Recovery Course not being quite so popular as it used to
be
> > (and can't you just tell from some of the posts here of late?!), I may
be a
> > bit out of touch with RMAN... but here goes for nothing...
> >
> > RMAN doesn't "compress" backups, if by "compression" you're thinking of
> > anything like WinZip or gzip.
> >
> > Being an Oracle utility, however, it is intelligent enough to realise
when a
> > block on disk has never been used (ie, is above a high watermark
somewhere),
> > and will not include such blocks in the output backup sets. That
contrasts,
> > of course, with O/S backups which, not having a clue what they are
actually
> > copying, take a byte for byte copy of the physical datafile, unused
blocks
> > and all. Net result: RMAN backup sets are significantly smaller than a
> > physical backup simply using O/S copy commands would be.
> >
> > RMAN makes things even smaller when you do incremental level backups:
again,
> > because it understands Oracle blocks and data structures, it can tell
> > whether a block has changed since the last backup... if it has, it gets
> > included in the backup set. If not, it doesn't -and once again, such
> > omission makes the resultant backup set much smaller than it otherwise
would
> > be.
> >
> > If there is actually an RMAN command to compress a backup set a la
WinZip,
> > I'm not aware of it, and frankly I'd be gobsmacked ...Oracle generally
takes
> > the view that you play around with compression utilities at your peril.
> > It's valuable data, after all.
> >
> > Regards
> > HJR
> >
> >
> >
> > "Ted Chyn" <ericis6_at_home.com> wrote in message
> > news:Bhlj7.139845$oh1.55982353_at_news2.rdc2.tx.home.com...
> > > sir, Can anybody shed light on how rman compress the datafile during
> > backup
> > > ?
> > > thnx ted chyn
> > >
> > >
Received on Thu Aug 30 2001 - 15:28:31 CDT
