Re: RDBMS Feature Matrix (FAQ in the works !!!)

In article <1993Mar22.151030.18234_at_ryn.mro4.dec.com>, abbott_at_priory.enet.dec.com (Robert Abbott) writes:
|>
|> In article <1993Mar19.004530.6969_at_mic.ucla.edu>, ddruker_at_agsm.ucla.edu
|> (Daniel Druker) writes...
|> >
|> >I thought it might be useful to maintain an On-Line feature comparison
|> >matrix of the various major RDBMS products as part of a
|> >comp.databases.* faq. It seems to be a repeated theme that people ask
|> >for such comparisons and I haven't seen a good one yet.
|> >
|>
|> Among the long list of features I have extracted these three.
|> I think I understand shared and multiplexed log files (and how
|> that is basically the same thing.) What I don't understand
|> is the multiple log files.
|>
|> Are you saying that Oracle (v7 ?) allows you to configure
|> multiple REDO log files (for the same database) all of which
|> can be used simultaneously? I am aware of how multiple files
|> can be configured into a single logical file and how they are
|> used serially, but that's not what I would call multiple log
|> files since only one file is active at any time.
|>
|> >10. Shared Log Files Y
|> >37. Multiplexed Log Files Y
|> >46. Multiple Log Files Y
|> >
|> ------------------------
|> Robert K. Abbott
|> abbott_at_tps.enet.dec.com

Multiplexed redo log files allow the same redo log information to be written simultaneously to two or more online redo logs. This is a new feature of Oracle7. In order to use this feature you create a logfile "group" and place the indivdual log files in the group. When lgwr performs the write, it writes to all the files in the group simultaneously. The idea of course is to place each member of a logfile group on a different disk. Of course you will need at least two separate groups of logfiles in order for a log switch to be performed.

                       Ian MacGregor
                       Stanford Linear Accelerator Center
                       (415) 926-3528