RE: parallel recovery slaves waiting on undo reads

From: Noveljic Nenad <nenad.noveljic_at_vontobel.com>
Date: Thu, 27 Feb 2020 11:51:15 +0000
Message-ID: <22455_1582804294_5E57AD46_22455_483_1_6f322fca74e34485902612e918f7031a_at_vontobel.com>

The half of the reads are indeed on only three index partitions:

SQL> select obj#,dataobj#,value,100*ratio_to_report(value) over() perc from v$segstat where statistic_name = 'physical reads' order by value desc fetch first 5 rows only ;

      OBJ# DATAOBJ# VALUE PERC
---------- ---------- ---------- ----------
4294967295 35894092 10644378 18.892159 4294967295 35894903 9141720 16.2251686 4294967295 35894891 8487867 15.0646786 4294967295 35894096 2833553 5.02912748 4294967295 35894095 2719772 4.82718344

Executed on the primary database:

SQL> select data_object_id, object_type from dba_objects where data_object_id in ( 35894092, 35894903, 35894891, 35894096, 35894095 );

DATA_OBJECT_ID OBJECT_TYPE
-------------- -----------------------

      35894092 INDEX PARTITION
      35894095 INDEX PARTITION
      35894096 INDEX PARTITION
      35894891 INDEX PARTITION
      35894903 INDEX PARTITION

Many thanks,

Nenad

https://nenadnoveljic.com/blog/

-----Original Message-----

From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> On Behalf Of Jonathan Lewis Sent: Donnerstag, 27. Februar 2020 11:08 To: oracle-l_at_freelists.org
Subject: Re: parallel recovery slaves waiting on undo reads

In general I would expect it to be indexes that are the target for "db file parallel read", but possiby parallel recovery processes are allowed to behave completely differently.

Regards
Jonathan Lewis

---

From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on behalf of Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk> Sent: 27 February 2020 10:04
To: oracle-l_at_freelists.org
Subject: Re: parallel recovery slaves waiting on undo reads

Can you get access to v$segstat / v$segment_statistics to see what's changing most ?

Regards
Jonathan Lewis

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http://www.freelists.org/webpage/oracle-l Received on Thu Feb 27 2020 - 12:51:15 CET