I guess this test was in response to a claim that
'you have to put your log files on the
inner/outer/middle section of the disc
for best response time.'
I think this demonstrates that there are never any
easy answers - and rarely any conclusive tests
other than real-life.
One thing you
BTW - this is not a fair test of normal OLTP activity -
some experiments I've been doing recently suggest
that inside a PL/SQL loop the COMMIT does not
cause a log file sync - if you check your
redo synch writes
and
redo writes
statistics, you may find that redo synch
Out of curiosity and as a test I scrubbed my 16Mb RAID1 array and set it up
again with 5 x 50Mb redo groups. I ran the following script to generate
lots of redo:
begin
for i in 1..1500 loop
insert into test_table values (mod(i,10));
delete from
Bill Buchan wrote:
Out of curiosity and as a test I scrubbed my 16Mb RAID1 array and set it up
again with 5 x 50Mb redo groups. I ran the following script to generate
lots of redo:
begin
for i in 1..1500 loop
insert into test_table values (mod(i,10));
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Hi
Yes you can untill the day that you have this runaway process that creates
20Gb of redo and than crashes your database 5 minutes before the daily
offline backup should kick in.
But you are only mirroring, why not put your database in
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You can only have a max of 8 log groups if I remember correctly.
Yesterday's backup may have failed, and you may have to recover from the day
prior or prior's prior. Keep this in mind as well.
With archive log, you can use 6 month old backup,
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Hi
Thanks. That's a very good point. I agree that ARCHIVELOG mode will be
needed.
However, I still have this big disk just for redo logs, so I'm tempted to
fill it anyway. This will be a sort of supplementary backup in case the
archive disk
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It is very common for people to see all that free space and want to fill it.
Avoid the desire, fill it with a blank file. Disks are cheap and if you
store things on the outer platters performance will suffer.
Redo logs and other things in oracle
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Christopher R. Spence said:
You can only have a max of 8 log groups if I remember correctly.
Gee, I thought that the DBA controlled the maximum number of redo logs
allowed for a database.
There's this thing called a database create statement:
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Generally IDE shows this problem much more than scsi, but on IDE you can see
as much as 50% performance degrading, I haven't really tested the
difference.
If you put the logs on, then fill the rests of the disks with a empty file
of that size, you
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Christopher R. Spence said:
Disks are cheap and if you store things on the outer platters performance
will suffer?
Chris, I'm not sure what you mean here.
The concept of Variable Transfer Rate covers this.
Stealing a quote from: Optimal Storage
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How big a performance issue is the location of the log file on disk? Even
if I create the minimum of 2 archive log groups, how can I be sure the
controller hasn't put these on the outer platters anyway? Since these are
log files then the
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I forgot the word default; I know 8 used to be the default. I tend to be
doing many different things when I respond to emails. I guess it would be
much easier if I didn't post at all. Not like I ever ask questions on the
list.
But thanks for
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AIX has a unique concept of this.
Given data spread on a disk. The head will spend more time over the
middle tracks as it seeks data that is distributed across the disk.
Thus for faster access, place your tablespace on the middle tracks
of a
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Excellent. Thanks for the information; maybe I won't fill my whole disk
with redo now!
- Bill.
At 08:40 14/09/01 -0800, you wrote:
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Generally IDE shows this problem much more than scsi, but on
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I think that Chris was referring to the maximum number of redo log group one
COULD create - an Oracle hard limit. I don't know what it is, but I know its
not 8 since I have created OPS databases with 12 redo groups for each instance
and multiple
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It is default to 8, unless you change it by rebuilding the control file or
init.ora, depending on the version.
Although 8 is platform dependant.
Do not criticize someone until you walked a mile in their shoes, that way
when you criticize them,
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Christopher - I for one appreciate your efforts to share your knowledge. I
suppose that like most of us you have employment in addition to this list.
The best most of us can manage is to jot off a quick reply without benefit
of extensive research.
, September 14, 2001 10:45 AM
To: Multiple recipients of list ORACLE-L
Subject: RE: Lots and lots of redo logs
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AIX has a unique concept of this.
Given data spread on a disk. The head will spend more time over the
middle tracks as it seeks data
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I love it when people explain their hypotheses - it makes
it so much easier to understand why two people can
apparently contradict each other and still be right.
Presumably the argument for putting the data at the
outside edge (could still be)
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