Re: FTS waiting on db file sequential reads?
- From: Riyaj Shamsudeen <riyaj.shamsudeen@xxxxxxxxx>
- To: k3nnyp@xxxxxxxxx
- Date: Thu, 18 Sep 2014 13:07:05 -0700
Hello Chris
Snapper should also spit out statistics for 'table fetch continued row'
if you use gather=stw. Could you post the full output of snapper with
gather=stw? That will give us more data.
Second, AFAIK, full table scan should not follow the chain for migrated
rows, except in the case of inmemory population:
https://orainternals.wordpress.com/2014/09/11/inmemory-why-didnt-that-table-was-populated-in-the-column-store/
Yes, dbms_stats doesn't populate chain_cnt. You must use analyze table..
Another possibility is that may be the buffer cache already has blocks of
the table cached and so, single block reads are performed.
Cheers
Riyaj Shamsudeen
Principal DBA,
Ora!nternals - http://www.orainternals.com - Specialists in Performance,
RAC and EBS
Blog: http://orainternals.wordpress.com/
Oracle ACE Director and OakTable member <http://www.oaktable.com/>
Co-author of the books: Expert Oracle Practices
<http://tinyurl.com/book-expert-oracle-practices/>, Pro Oracle SQL,
<http://tinyurl.com/ahpvms8> <http://tinyurl.com/ahpvms8>Expert RAC
Practices 12c. <http://tinyurl.com/expert-rac-12c> Expert PL/SQL practices
<http://tinyurl.com/book-expert-plsql-practices>
<http://tinyurl.com/book-expert-plsql-practices>
On Thu, Sep 18, 2014 at 12:31 PM, Kenny Payton <k3nnyp@xxxxxxxxx> wrote:
> Look at the "analyze table list chained rows" command. It could be
> chained or migrated rows.
>
> We have pretty bad re-occurring migrated rows from time to time and have
> to reorg occasionally to get rid of them. Oracle added a feature to 12.?
> and 11.2.0.4 that gives you some control over migrated rows. The problem
> apparently raised its head during some Exadata performance proofing.
>
> Kenny
>
>
>
> On Thu, Sep 18, 2014 at 3:25 PM, Chris Taylor <
> christopherdtaylor1994@xxxxxxxxx> wrote:
>
>> The last analyzed date (yesterday) shows CHAIN_CNT = 0 but I'm not
>> positive that is accurate. (Seems like I remember you have to check a
>> different way to get an accurate picture of chained or migrated rows)
>>
>> Chris
>>
>> On Thu, Sep 18, 2014 at 2:18 PM, Wolfgang Breitling <
>> breitliw@xxxxxxxxxxxxx> wrote:
>>
>>>
>>> - chained rows
>>> - delayed block clean out
>>>
>>>
>>>
>>>
>
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