Re: Question about ARCHIVELOG mode

"agis" <stag_at_hq.acn.gr> escribió en el mensaje news:cjjjq5$88f$1_at_ulysses.noc.ntua.gr...
>
> "Ed Stevens" <nospam_at_noway.nohow> wrote in message
> news:o1kql01sauvc19d71e1nl1cg5bo4c6qm6p_at_4ax.com...
> > On 1 Oct 2004 01:29:20 -0700, pyzhykea_at_belhard.com (Eugene Pyzhyk)
> > wrote:
> >
> >>Hello all!
> >>
> >>Can you help me ?
> >>
> >>Does anybody know, may I start Oracle Server in ARCHIVELOG mode and
> >>perform redo logs archiving in manual mode (only when I want to
> >>archive it). Or automatic redo logs archiving must be enabled for
> >>correct Oracle Server functioning ?
> >>
> >>Thank you!
> >>
> >>Eugene Pyzhyk
> >
> > If you are manually archiveing, what do you think Oracle is going to
> > do when all of the on-line archive logs are full and you aren't
> > Johnny-on-the-spot to issue your manual archive command? In short,
> > why would you even consider manual archiving?
>
>
> This is not a posibility ...
>
> 1) There are not online archive logs Archive logs are archived redo logs
>
> 2) Redo log is a cycling mechanism in simple words. In manual archive mode
> it will operate the same way as in noarchivelog mode !!! until a command
> archives the logs !!!!
>
> I agree with u that archivelog mode MUST always be automatic in order to
> recover the database !!!!
>

I think point 2 may need to be clarified slightly.

If the database is in archivelog mode with automatic archiving disabled then you can (quite quickly)
reach a situation where all online redo log groups are filled, but not yet archived, thus causing the
database to hang. Once the logs are archived (ALTER SYSTEM ARCHIVE LOG ALL), normal
service is resumed. This is quite easy to verify- issue ALTER SYSTEM SWITCH LOGFILE.
See how many times you can do it before the DB locks.

As Ed Stevens has pointed out, having automatic archiving disabled will require a constant
watch on the state of the redo logs.

BTW: Automatic archiving has nothing to do with DB recovery. The only archivelog requirement
for recovery is the availability of ALL archived logs between the backup and the required recovery
point.

HTH
Anthony Hogan Received on Fri Oct 01 2004 - 08:38:29 CDT