Re: When does LGWR flush the ebuffer?

On Tue, 22 Apr 2003 23:30:44 +1000, "Richard Foote" <richard.foote_at_bigpond.com> wrote:

>"Peter" <peter_at_nomorenewsspammin.ca> wrote in message
>news:kur9avoueoqsaaepunact06qcraj7vla7o_at_4ax.com...
>>
>> The LGWR flushes the buffer every 3 seconds, or when there is a
>> commit.
>> Does it ever flush it when the buffer is 1/3 or totally full?
>> If it flushes it when buffer 1/3 full, then it will never get filled
>> up?
>>
>Hi Peter,
>
>The following wakes up LGWR:
>
>- a commit
>- redo log buffer reaching 1/3 full or 1M (whichever comes first)
>- when DBWR wakes up (such as every 3 seconds, checkpoint, etc.)
>

A logswitch would also trigger a checkpoint and in turn a flush of redo log?

Thanks a lot

>If you have a bucket with a hole in it which you cover with your finger
>until the bucket is 1/3 full, does that mean the bucket will never get full
>?
>
>Will that kinda depends on how "turned on" the tap is and how quickly water
>enters the bucket. If water enters at a faster rate than the water leaves
>the bucket via the hole, then yes, eventually the bucket can and will fill
>up.
>
>Same for the redo log buffer. In fact, it's potentially a little worse in
>that until the 1/3 is written out, Oracle can't overwrite that region of the
>buffer. So if your buffer is sized too small, this event can eventuate.
>
>Cheers
>
>Richard
>
Received on Tue Apr 22 2003 - 14:18:16 CDT