Re: How to resize redo logs

You can also query the database to determine how often the redo logs are switching. There are several flavors of the script below, but this one will calculate the average log switches per day.

• avg redo switches per day select round(avg(count(*))) from v$loghist group by to_char(first_time,'J');

mreeves

On Fri, 2 Feb 2001 08:02:13 +1100, "Howard J. Rogers" <howardjr_at_www.com> wrote:

>They should be as big as are needed to get log switches happening at the
>"right" interval.
>
>Huge log files will take ages to fill, and you will therefore log switch
>infrequently. Since there is a major checkpoint at each log switch, that
>means you avoid having one hell of an i/o fest. Performance therefore goes
>up a bit. Since Instance Recovery means Oracle replays all transactions
>since the last checkpoint, however, then huge log files mean longer Instance
>Recoveries.
>
>Tiny log files will fill rapidly, and will therefore switch like crazy -lots
>of checkpoints, poor performance, but good Instance Recovery times.
>
>Your mission is to find somewhere along that spectrum where you can be
>happy. The usual 'rule of thumb' that a lot of DBAs adopt is to arrange for
>the files to be big enough that they switch every half-hour to an hour, on
>average. But that may well not be what is suitable in your particular case.
>
>You can check how often you are log switching by checking the Alert Log.
>Messages such as "Thread 1 advanced to Log Sequence 15634" indicate a log
>switch.
>
>If you ever see a message to the effect that "Thread 1 unable to advance to
>Log Sequence 15635", then it means you haven't got *enough* redo log groups
>(the size of them having little or no bearing on that particular message).
>
>Regards
>HJR
>
>
><MAbbouchi_at_IITRI.ORG> wrote in message
>news:DD42667CBCE4D3119D0700104B95123F3016CA_at_abmail.iitri.org...
>> How to resize redo logs and is there a special consideration to be aware
 of?
>>
>> Thanks
>> Mo
>>
>> --
>> Posted from nat05.IITRI.ORG [205.167.170.5]
>> via Mailgate.ORG Server - http://www.Mailgate.ORG
>
>
Received on Thu Feb 01 2001 - 15:32:45 CST