Re: dba_tab_mod view

From: Mladen Gogala <>
Date: Wed, 13 May 2015 14:54:19 -0400
Message-ID: <>

Yes, the manual does say so, and I am aware of that. However, the manual is not always correct:

    Connected to:
    Oracle Database 11g Enterprise Edition Release - 64bit     Production
    With the Partitioning, OLAP, Data Mining and Real Application     Testing options

    SQL> select count(*) from dba_tables where monitoring='YES';



    SQL> select count(*) from dba_tables;


    SQL> select count(*) from dba_tables where monitoring='NO';



There is a significant number of tables without the monitoring attribute, despite the fact that it is 11G and that the statistics level is "ALL" (development database, I want plan statistics for every plan).

    SQL> show parameter statistics_level

    NAME                     TYPE  VALUE
    ------------------------------------ -----------
    statistics_level             string  ALL
    SQL> There is also a possibility that the table was created by using DDL generated from Oracle 10G, with the "NOMONITORING" clause, in which case an explicit setting will take precedence over the default. Long story short, I always check the "MONITORING" attribute when dealing with DBA_TAB_MODIFICATIONS. One reason to make sure this is set is playing with the stale percent attribute. If you don't want a table frequently analyzed for any reason whatsoever, you can set stale percent to 99% and, in case of a very large table, have it always skipped. I did that because I have manually set clustering factor for one of the indexes, to make range scans less expensive. I know all about the best practices and am fully aware that this is not one of them.

On 05/13/2015 09:46 AM, Deas, Scott wrote:
> Since OP mentioned that he was on 11.2, the setting of this value at a
> table level has been deprecated and is now controlled via the
> STATISTICS_LEVEL of the database -
> If the STATISTICS_LEVEL is set to TYPICAL (default) or ALL, monitoring
> is enabled by default. Only if the OP had his database’s
> STATISTICS_LEVEL parameter set to BASIC would he not have any
> monitoring enabled.
> Thanks,
> Scott
> *From:*
> [] *On Behalf Of *Mladen Gogala
> *Sent:* Tuesday, May 12, 2015 9:38 PM
> *To:*
> *Subject:* Re: dba_tab_mod view
> Also, that will only work for tables that have MONITORING attribute set.
> On 05/12/2015 10:48 AM, Deas, Scott wrote:
> Ram,
> After you issue DML, but before you run statistics, you can run
> dbms_stats.flush_database_monitoring_info to update the views.
> Thanks
> Scott
> *From:*
> <>
> [] *On Behalf Of *Ram Raman
> *Sent:* Monday, May 11, 2015 7:13 PM
> *To:* ORACLE-L
> *Subject:* dba_tab_mod view
> List,
> After seeing lots of global services enqueue deadlock errors in
> our rac, I was looking up the trace files. I was able to see the
> sql; the trace files are huge (in GBs) . The sql was simple and
> was updating one table only repeatedly. I wanted to know how many
> updates had happened in the table, but the dba_tab_mod view is
> empty for that table. The table was last analyzed last night. Does
> this mean that the updates did not happen at all due the deadlock
> errors?
> To my knowledge, the DTM view is emptied out after a stats
> collection. Is there anything else that would cause the no rows
> selected for a table from that view. v11.2
> Ram.
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Mladen Gogala
Oracle DBA

Received on Wed May 13 2015 - 20:54:19 CEST

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