Re: Performance issues when running in archive redo log mode

A copy of this was sent to "Birsan" <adrianbirsan_at_sprint.ca> (if that email address didn't require changing) On Wed, 3 Nov 1999 04:01:08 -0800, you wrote:

>One of the consultants that we are working with claims that their tests have
>consistently shown that there is a significant performance hit when ORACLE 7
>(running on UNIX, different flavors, one of them being NCR UNIX), is set to
>operate in archive redo log, as oposed to non archive redo log, mode (the
>performance hit is said to be 30-40%). This confuses me, because I had the
>obvious misconception that the only difference (as long as you do not
>actually issue "alter tablespace begin backup") is that you do not re-use
>the redo logs, but "archive" them, so that they can be used later in the
>recovery process. I certainly did not expect such a big hit, which basically
>stops us from using normal on-line backup procedures, even though
>availability has to be 7x24. For performance reasons as well, the consultant
>recommends not using replication either, which leaves us with the only
>choice of a proprietary application replication scheme, in order to provide
>high availability and database maintenance capabilities (provided by the
>consultant). Can anyone confirm that these claims make sense?
>Thank you for your response!
>

running in archive log mode will not materially affect database performance.

The database is not doing any extra work (the OS is -- there is the archive process running and its doing work). The OS will have to copy the redo from one device to another.

The consultant sounds like he is out to make some money by writing a custom replication scheme. Wonder how they could write a faster one then the one that is in the database kernel itself?

Get a new consultant. One that knows how to setup disks to avoid contention between LGWR and ARCH (trivial) and run archive log mode. All production systems that care about their data run in archive log mode.

--
See http://osi.oracle.com/~tkyte/ for my columns 'Digging-in to Oracle8i'... Current article is "Part I of V, Autonomous Transactions" updated June 21'st  

Thomas Kyte                   tkyte_at_us.oracle.com
Oracle Service Industries     Reston, VA   USA

Opinions are mine and do not necessarily reflect those of Oracle Corporation Received on Wed Nov 03 1999 - 07:40:32 CST