Re: Q: redo bytes statistics is it sum of all members or not ?
- From: amihay gonen <agonenil@xxxxxxxxx>
- To: jonathan@xxxxxxxxxxxxxxxxxx
- Date: Wed, 25 Jun 2014 15:35:33 +0300
ok , according to this , oracle doesn't have a clear metric how many redo
bytes where actually written to disk .
what i can do it to multiple redo blocks written* blk size*member_count .
( making sure that all members are valid and not stale).
On Wed, Jun 25, 2014 at 3:07 PM, Jonathan Lewis <jonathan@xxxxxxxxxxxxxxxxxx
> wrote:
>
> Physical Write Bytes is the "logical" bytes for blocks written by DBWR.
>
> Physical write total bytes is EVERYTHING else - including every copy of
> the redo logs written by LGWR, control file writes and data files writes
> from CKPT, control file writes from MMON, archived redo log writes from
> ARC0, direct path writes and local writes from foreground sessions etc...
>
>
>
>
> Regards
> Jonathan Lewis
> http://jonathanlewis.wordpress.com
> @jloracle
> ------------------------------
> *From:* amihay gonen [agonenil@xxxxxxxxx]
> *Sent:* 25 June 2014 12:48
> *To:* Jonathan Lewis
> *Cc:* ORACLE-L
>
> *Subject:* Re: Q: redo bytes statistics is it sum of all members or not ?
>
> thanks for the quick response.
>
> I still don't understand . that stat : physical write total
> bytes according to oracle doc is
> "Total size in bytes of all disk writes for the database instance
> including application activity, backup and recovery, and other utilities.
> The difference between this value and "physical write bytes" gives the
> total write size in bytes by non-application workload."
>
> 1. is this metric means all writes (include dbwr writes ) ?
> 2. if I reduce physical write total bytes-physical write bytes it will be
> equal to redo size+ redo wastage ? is lgwr part of application work load .
> 3. is the answer to 1 is true , the mulitple "physical write total bytes"
> * redo_memebers_number , won't give correct answer.
>
> thanks for your time,
> amihay
>
>
>
>
>
>
> On Wed, Jun 25, 2014 at 1:39 PM, Jonathan Lewis <
> jonathan@xxxxxxxxxxxxxxxxxx> wrote:
>
>>
>> You're correct.
>> You could think of it as a "logical" measure of redo generated and
>> written.
>>
>> When you look at the stat physical write total bytes", that's when you
>> have to multiple by the number of copies before adding to the total, and
>> don't forget that "redo blocks written" is derived from "redo size" + "redo
>> wastage".
>>
>>
>>
>>
>> Regards
>> Jonathan Lewis
>> http://jonathanlewis.wordpress.com
>> @jloracle
>> ------------------------------
>> *From:* oracle-l-bounce@xxxxxxxxxxxxx [oracle-l-bounce@xxxxxxxxxxxxx] on
>> behalf of amihay gonen [agonenil@xxxxxxxxx]
>> *Sent:* 25 June 2014 11:09
>> *To:* ORACLE-L
>> *Subject:* Re: Q: redo bytes statistics is it sum of all members or not ?
>>
>> some question for "redo size" statistic as well
>>
>> thanks .
>>
>>
>> On Wed, Jun 25, 2014 at 12:51 PM, amihay gonen <agonenil@xxxxxxxxx>
>> wrote:
>>
>>> Hi DBA's - quick question
>>>
>>> According to my tests the statistic "redo blocks written" is not a
>>> sum of redo block written to *all *redo memebers.
>>>
>>> I've run test with instance with 2 members and then with 3 members and
>>> this metric didn't change.
>>>
>>> but just to make sure I didn't missed something :)
>>>
>>> I wander if anyone has test it and can approved this conclusion .
>>>
>>>
>>>
>>>
>>> thanks ,
>>> amihay
>>>
>>
>>
>
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