Re: log_buffer sizing
- From: Stefan P Knecht <knecht.stefan@xxxxxxxxx>
- To: "kp0773@xxxxxxxxx" <kp0773@xxxxxxxxx>
- Date: Tue, 16 Aug 2011 07:20:40 +0200
And in addition to Tim's reply - how many redo log groups are there?
Adding more groups can give the archivers an additonal buffer to do their job
during peaks.
Stefan
On 16.08.2011, at 01:13, K R <kp0773@xxxxxxxxx> wrote:
> Tim,
>
> once in a while we see wait on the toad ( log file waiting to be archived )
> and as the log buffer is only 20MB and the online logs are 3GB so we were
> discussing if we can do as per any recommended sizing .
>
> Thanks
> Kart
>
> On Mon, Aug 15, 2011 at 1:12 PM, Tim Gorman <tim@xxxxxxxxx> wrote:
> Kart,
>
> There is no magic bullet in that query, it was just for your information, so
> you can provide something more useful than the size of your online redo log
> files.
>
> So, asking again: what are you seeing that made you say, "the log buffer
> seems too small". From this query, you can see when redo generation gets
> high. During those times, are you seeing anything that indicates any kind of
> "bottleneck" in redo processing?
>
> Thanks!
>
> -Tim
>
> -----Original Message-----
> From: K R [mailto:kp0773@xxxxxxxxx]
> Sent: Monday, August 15, 2011 02:01 PM
> To: tim@xxxxxxxxx
> Cc: Oracle-L@xxxxxxxxxxxxx
> Subject: Re: log_buffer sizing
>
> Tim,
> this is a typical workload when the batch is running on the database.
>
> DAY HR NBR_SWITCHES GB
> ----------- ----- ------------ -----------
> 13-AUG-2011 00:00 12 3.84
> 01:00 12 8.46
> 02:00 30 51.52
> 03:00 38 60.86
> 04:00 36 61.56
> 05:00 43 72.49
> 06:00 43 55.48
> 07:00 12 0.45
> 08:00 12 0.03
> 09:00 12 0.26
> 10:00 12 6.42
> 11:00 12 3.89
> 12:00 12 0.25
> 13:00 12 2.35
> 14:00 12 0.04
> 15:00 13 1.90
> 16:00 41 72.73
> 17:00 32 55.27
> 18:00 37 44.95
> 19:00 12 0.10
> 20:00 12 0.05
> 21:00 12 0.05
> 22:00 12 3.65
> 23:00 14 16.64
> *********** ***** -----------
> sum 523.25
>
>
>
> On Mon, Aug 15, 2011 at 12:52 PM, Tim Gorman <tim@xxxxxxxxx> wrote:
> Kart,
>
> What exactly are you seeing in the database that makes you say "it just seems
> too low"?
>
> Bear in mind that the size of the online redo log files has no causal
> relation to the size of the log buffer, and vice-versa. What matters is the
> rate with which redo is written, and the frequency of COMMIT commands by the
> application.
>
> For the first bit of information, try the following SQL*Plus script...
>
> clear breaks
> break on day skip 1 on hr on report
> compute sum of gb on day
> compute sum of gb on report
> col sort0 noprint
> col cnt format 999,990
> col gb format 999,990.00
> select trunc(completion_time,'HH24') sort0,
> to_char(trunc(completion_time,'HH24'),'DD-MON-YYYY') day,
> to_char(trunc(completion_time,'HH24'),'HH24')||':00' hr,
> inst_id,
> count(*) nbr_switches,
> sum(blocks*block_size)/(1048576*1024) gb
> from gv$archived_log
> group by trunc(completion_time,'HH24'),
> to_char(trunc(completion_time,'HH24'),'DD-MON-YYYY'),
> to_char(trunc(completion_time,'HH24'),'HH24')||':00',
> inst_id
> order by 1, 2, 3, 4;
>
> That will give you some idea of the rate and volume. Of course, this query
> may end up double-counting redo volumes if you have additional archive
> destinations set up, so be aware of that and adjust accordingly.
>
> Hope this helps...
>
> Thanks!
>
> -Tim
>
>
> -----Original Message-----
> From: K R [mailto:kp0773@xxxxxxxxx]
> Sent: Monday, August 15, 2011 01:22 PM
> To: Oracle-L@xxxxxxxxxxxxx
> Subject: log_buffer sizing
>
> All ,
>
> my online redo logs are 3G . This is a batch intensive datawarehouse
> application. What should i be keeping my log_buffer .
>
> currently it is set at 29425664 and it just seems too low .
>
> thanks
> Kart
>
>
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