RE: Optimized redo log access
Date: Sun, 17 Aug 2014 09:13:00 -0400
Message-ID: <135101cfba1c$f98c5d10$eca51730$_at_rsiz.com>
I also do not know a way to make the archiver read a preferred member.
However, you may be able to get the read from a preferred physical disk depending on your volume manager.
In ASM this would be by setting (or your preference being the default) the asm preferred read failure group as shown in this example from the manual so that your preferred read is the first one:
alter system set asm_preferred_read_failure_groups = 'DG2.DG2_0000','DG3.DG3_0000'
In some other volume managers there are possibilities for influencing or controlling the preferred read of a volume constructed from plexes on different physical media.
The starting point recommendation for multiple members is they should be on media of similar capabilities and load, so the archiver (unless they slipped it in when I wasn’t paying attention) does not directly have a toggle for preference by member.)
Good luck. (Of course feeding arch is the reason some folks put redo on SSD, while benchmarkers run around “debunking” the idea of redo on SSD because they can show it does not speed up writes to compared to isolated physical HD volumes when they compare to flash SSD [not battery backed DRAM SSD] with arch turned off.) Removing arch reads from your diskfarm by relocating redo to SSD will in fact “deheat” your disk farm and remove the competition for seeks for writes and bandwidth for arch reads. Since redo is usually small relative to the database disk farm, this may be cost effective, depending on your situation.
mwf
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of xiangdongzou
Sent: Sunday, August 17, 2014 5:27 AM
To: agonenil; ORACLE-L
Subject: 回复: Optimized redo log access
archiver process can't read only special member.Oracle decicde which
member shoulde read.
2014-08-17
I AM AN ORACLE FANS! Skype:Frank.oracle
Email:xiangdongzou_at_gmail.com
发件人：amihay gonen <agonenil_at_gmail.com>
发送时间：2014-08-17 16:51
主题：Optimized redo log access
收件人："ORACLE-L"<oracle-l_at_freelists.org>
抄送：
Hi , I've system that have multiplex redo log (2 members per group) and multiplex destinations .
Due to performance consideration I would like to configuration the archiver process to read only from one member (to reduce load on the specific device).
I'm not aware of such option to tell oracle which member to read .
Does anyone know if it is possible ?
Amihay .
-- http://www.freelists.org/webpage/oracle-lReceived on Sun Aug 17 2014 - 15:13:00 CEST