Re: Are offline backups an option, or a neccessity?

Joel Garry wrote:

> In article <3479A131.EB5B671B_at_barakitc.co.il>,
> Muli Koppel <mkoppel_at_barakitc.co.il> wrote:
> >
> >
> >As one of the commentators already said - this issue worth a comment.
> >
> >If I'm wrong about my following statements - do not hesitate...
> >
> >1. Tablespaces are taking offline during Hot Backup. Any DML changes during
> >the copying of the tablespace's underlying files are written to the Redo Log
> >Files.
>
> Not a hot backup.
>
> ALTER TABLESPACE BEGIN BACKUP is an online, hot backup. Taking the tablespace
> offline is not a hot backup. Not bringing the db down is not a cold backup,
> either.
>
> >
> >2. To Guarantee 100% of sucessful Hot Backup, these Redo Logs should be backed
> >up as well.
> >
> >3. Therefore, we're doing Hot Backups - and only hot backups - everyday, doing
> >the
> >following :
> >
> > - taking each tablespace offline & backing its files
>
> Um, how exactly are you doing this? If you are OFFLINE NORMAL, what about
> users that are on? If the users cannot use the tablespace (and they can't,
> for example, allocate sort space), then how is it a hot backup? It's kind
> of lukewarm, since it allows separate spaces to be backed up at different
> times, but doesn't allow users to access the database. Which is the point
> of hot backups.
>
> > - and then :
> > - find out current log file
> > - alter system switch log file
> > - alter database backup control file to 'backup area'
> > - copying switched log file to 'backup area'
> >
> >This way a complete database resotre is possible, rolling forward only archive
> >logs that
> >were created since the very beginning of the backup untill crash has happened.
>
> The other alternative to the original question of 3X disk versus cold
> backups, is archivelog to tape. But then you'd have to buy more tape drives,
> and pay a lot for the resulting high ops costs. Tape is a prettttty
> funnnnnnky medium. One misaligned tape head and there go all those carefully
> organized backups. But you don't know it until it is too late, after
> the maintenance on the tape drive.
>
> >
> >Yours,
> >
> >Muli Koppel
> >
> --
> These opinions are my own and not necessarily those of Information Quest
> jgarry@eiq.com http://www.informationquest.com
> http://ourworld.compuserve.com/homepages/joel_garry
> "See your DBA?" I AM the @#%*& DBA!

  A slip of the tongue : Tablespace, of course, is not entered into an OFFLINE state,

otherwise it is not a Hot Backup.

So it shouldn't be "taking tablespace offline" but rather "begin backup - copy - end

backup".

George Dau's remark, about coopying also all archive logs is correct as well. That's why

i mentioned in case of recovery we need to roll all archives from the very beginning of the

backup - that means, they should be backed-up as well, as we do.

so long.

.

.

. Received on Tue Nov 25 1997 - 00:00:00 CST