RE: Global Stats

Kirti:

I think the interval is changed to 5 minutes from 3 hours starting from 9i (rel2?).

Best Regards,
K Gopalakrishnan

-----Original Message-----
Kirti
Sent: Wednesday, January 29, 2003 8:19 PM To: Multiple recipients of list ORACLE-L

Lisa,
 Monitoring, by itself, does not fire any automatic analyze. It simply montiors the DML activity on the monitored table and counts inserts/deletes/upates. Those counts may not be 100% accurate, but are very close. These can be viewed in dba_tab_modifications, and are dumped there by SMON every 3 hours or so (in 9i there is a new procedure, flush_database_monitoring_info, to flush these counts to this view on demand). These counts do not affect the ones maintained in *_tables views.

Monitoring is basically there to help identify which tables may need statistics computed again. 'Gather stale' option will only analyze tables that have undergone DML activity (inserts/deletes/updates) that amounts to more than 10% of the number of rows (from previous analyze) in the table. And 'gather auto' option 'figures' out what tables to analyze, but you must execute dbms_stats. So, there is nothing automatic in gathering table stats.

You can test it yourself..... remember there is a last_analyzed column ;)

HTH,

• Kirti

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

From:	Koivu, Lisa [mailto:Lisa.Koivu_at_efairfield.com]
Sent:	Wed 1/29/2003 9:09 AM
To:	Multiple recipients of list ORACLE-L
Cc:
Subject:	RE: Global Stats

Hi Jared,

Actually I think monitoring won't work in my case. Data loads fire throughout the day and the docs say that in 8i, analyze can fire based upon table monitoring sometime within 3 hours after data changes. I would rather include a manual fire of analyze in my data load and avoid any locking issues or contention for resources.

In addition, if temp space is blown during "auto-analyze" (fired based upon monitoring), would I know about it?

Just my thoughts. Am I wrong?

Lisa

-----Original Message-----
Sent: Wednesday, January 29, 2003 3:55 AM To: Multiple recipients of list ORACLE-L

You may want to read up on table monitoring.

Jared

On Tuesday 28 January 2003 11:10, Koivu, Lisa wrote:
> Hi everyone,
>
> Back to the lovely world of Oracle :) I've been reading up on statistics.
> Out of the 8.1.7 doco:
> /*
> Partitioned schema objects may contain multiple sets of statistics. They
> can have statistics which refer to the entire schema object as a whole
> (global statistics), they can have statistics which refer to an individual
> partition, and they can have statistics which refer to an individual
> subpartition of a composite partitioned object.
>
> Unless the query predicate narrows the query to a single partition, the
> optimizer uses the global statistics. Because most queries are not likely
> to be this restrictive, it is most important to have accurate global
> statistics. Intuitively, it may seem that generating global statistics
from
> partition-level statistics should be straightforward; however, this is
only
> true for some of the statistics. For example, it is very difficult to
> figure out the number of distinct values for a column from the number of
> distinct values found in each partition because of the possible overlap in
> values. Therefore, actually gathering global statistics with the
DBMS_STATS
> package is highly recommended, rather than calculating them with the
> ANALYZE statement
>
> */
> The table I need to generate stats for is currently 32GB and grows by ~2GB
> per week. Even the smallest estimate with calculating global stats will
> take a long long time and I may not be able to spring for all the required
> temp space.
>
> How does the list feel about global stats? Does anyone agree with the
> documentation that they "most important"? I'm thinking my partitioned
> statistics are the "most important".
>
> Any input is appreciated. Thanks
>
> Lisa Koivu
> Oracle Database Administrator
> Fairfield Resorts, Inc.
> 5259 Coconut Creek Parkway
> Ft. Lauderdale, FL, USA 33063

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Author: K Gopalakrishnan
  INET: kaygopal_at_yahoo.com

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