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.)
>
>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.
>

Now I see why. But is there any type of lock that Oracle places on the buffer while redo log is being flush.
It looks like filling continues while flushing is being done?

Thanks.   Received on Tue Apr 22 2003 - 13:24:34 CDT