I just thought I would mention a few other points ...
- Oracle's 1st recommendation is to use OS mirroring for REDO logs. I could
see debating this one and using the 2nd choice.
- The 2nd choice is to use Oracle's "mirroring" by specifying a 2nd member
in each REDO group.
- If you use OS mirroring, you shouldn't need the Oracle mirroring and the
opposite is true too.
- These REDO logs are the "hottest" (I/O) files in Oracle .
- You shouldn't put REDO logs on the same disk as tablespace files.
- Oracle writes and reads(if in archivelog mode) these files a lot but
sequentially and so the "best" choice is to put them on a OS mirrored file
system, not a RAID5 disk (which has a write "penalty").
- Specify more than just 1 or 2 groups if in archivelog mode. This allows
the LGWR (Log Writer) process time to copy the log before it is reused.
- REDO log sizes I have seen used are anywhere from 8Meg to 100Meg. In
media recovery, Oracle might take a little longer to apply the most recent
REDO log if large. But, a small size might generate too many archived logs .
Chucky <chuck.carson_at_syrrx.com> wrote in message news:<3E05D398.7010208_at_syrrx.com>...
> How would I add more logs per group on a database that has already been
> created and is up and running?
>
> Thx,
> CC
>
> Howard J. Rogers wrote:
> > "Chuckster" <chuckycarson_at_networkcloud.com> wrote in message
> > news:3E04A739.5020503_at_networkcloud.com...
> >
> >>When you have your redo logs created as follows:
> >>LOGFILE
> >> GROUP 1 '/u01/oradata/syrlims/redo01.log' SIZE 10M,
> >> GROUP 2 '/u02/oradata/syrlims/redo02.log' SIZE 10M,
> >> GROUP 3 '/u03/oradata/syrlims/redo03.log' SIZE 10M,
> >> GROUP 4 '/u04/oradata/syrlims/redo04.log' SIZE 10M
> >
> >
> > Correct. No redundancy. If you wanted redundancy, it would look like this:
> >
> > LOGFILE
> > GROUP 1
> > ('/u01/oradata/syrlims/redo1a.log','/u05/blahblahblah/redo1b.log') SIZE
> > 10M,
> > GROUP 2 ('/u02/oradata/syrlims/redo2a.log','/u06/bbb/redo2b.log') SIZE
> > 10M,
> > GROUP 3 ('/u03/oradata/syrlims/redo3a.log','/u07/bbb/redo3b.log') SIZE
> > 10M,
> > GROUP 4 ('/u04/oradata/syrlims/redo4a.log','/u08/bbb/redo4b.log') SIZE
> > 10M
> >
> > Extra groups buy you time before you start over-writing earlier logs (and,
> > specifically, buys ARCH time to archive the earlier logs before your try and
> > re-use them).
> >
> > Extra members per group buys you resilience and redundancy.
> >
> > And I've renamed your original files so that the number indicates the group
> > and the letter indicates the member, which I find easier to manage than the
> > 'official' recommendation of, for example, REDO0101 and REDO0102.
> >
> > Regards
> > HJR
> >
> >
> >>
> >>This is merely 4 different log files with no redundancy correct? If I
> >>wanted path redundancy, I would need to add more log files per group and
> >> make sure they are on different volume groups/spindles correct?
> >>
> >>Thanks,
> >>CC
> >>
> >>
> >>
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Received on Sun Dec 22 2002 - 13:05:13 CST
