Re: How to i check how often my redo logs switch??

Daniel Morgan <damorgan_at_x.washington.edu> wrote in message news:<1087799515.153873_at_yasure>...
> Edwinah63 wrote:
>
> > Hi everyone,
> >
> > hopefully easy questions!
> >
> > i have read in an Oracle manual that redo logs should be sized to
> > switch approx every 30 mins. unfortunately, said manual did not say
> > how to check how often it is switching.
>
> Sounds like nonsense to me. More one solution fits all mythology.
>
> > How do i check:
> > * how often my redo logs switch?
>
> SELECT *
> FROM v$log;
>
> SELECT *
> FROM v$log_history;
>
> > * how often my checkpoints occur?
>
> http://tahiti.oracle.com
>
> > * can i specify an interval to switch logs?
>
> No! Resize the log files if you think 30 minutes is some magical
> value ... it isn't.

Actually, the magical value is what granularity of time your management will agree that it is too expensive to not lose data. Since this is a sensitive question, 30 minutes is thought by some to be a reasonable compromise until a service level agreement is made.  

In DBA terms, it means the weak spot of Oracle's archiving is the loss of online logs. However much work is in there is how much you might lose. It is common IME to size log files to a time of maximum throughput (ie, batch updates or data loads, often with much smaller intervals due to hardware limitations) and have periodic alter systems to cycle the logs during more normal processing.

jg

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