Re: How keep 8i standby no-more-than 30 minutes behind?

"Howard J. Rogers" wrote:
>

<snip good synopsis of init.ora parameters>

> Unless, of course, you create a job (dbms_job is useful here, but you could
> do it from outside the database with cron) which issues an 'alter system
> switch logfile' every half hour. That way, regardless of whether the online
> log is practically empty (quiet time) or full (busy), the logs will switch
> and an archive will be produced, which can be shipped to the standby.

Right - but none of that *ensures* that the generated archive information is actually received *and applied* to the standby since 1) the primary archiver could fall behind and have multiple online redo's in need of archiving; 2) if MANDATORY isn't set in the log_archive_dest_n, the archive might not make it to the standby; 3) the standby might fall behind applying the redo, etc., etc. And without that guarantee, our friend Guy is sunk.  

> Of course, there is another answer: upgrade to 9i. There, you can configure
> the standby to lag the database by a specific number of minutes. But that's
> designed to *prevent* the application of shipped redo, to allow user errors
> to be corrected without the expense of an incomplete recovery. And that's
> not what you're after.

Ah, but 9i also allows you to use LGWR (as opposed to ARCH) to transport the redo data to the standby site, which allows for the possibility of no data loss and no data divergence - i.e. an Oracle guarantee that the standby is completely in sync with the primary (except, of course, for our old friends, the nologging transactions). So in sync, in fact, that if the primary can't write to the standby's redo logs, the primary shuts down immediately.

Regards,
Sean Received on Tue Mar 26 2002 - 22:43:01 CST