RE: dbms_stats

The reason why we switched from 'analyze table .. 10 percent' is because when we partitioned some of the huge tables, the query performance against these tables was really bad. 'Gather_table_stats' with size 2 on indexed columns did a much better job.

Have you had issues with 'analyze' against partitioned tables?

-----Original Message-----
Wolfgang Breitling
Sent: Wednesday, December 03, 2003 5:29 PM To: Multiple recipients of list ORACLE-L

In Oracle 8i you may as well stick with analyze since the dbms_stats call you use translates simply into a

   "analyze table ... ESTIMATE statistics sample 10 percent FOR TABLE FOR ALL INDEXES for all indexed columns size 2"

Why did you go from a simple analyze to gathering histograms on all indexed columns? I question the rationale of gathering histograms of "size 2". Aside from that, I question the rationale of a blanket histogram gathering (regardless of # of buckets) on "all indexed" or "all" columns. Histograms are like medicine. In the right (i.e. sparing dose) they are a therapeutic tool. In the wrong, especially too high dose, they become poison.

At 02:04 PM 12/3/2003, you wrote:
>Hello,
>
>Oracle 8.1.7.4 on HP-UX 11i
>
>A week ago, we replaced 'analyze table ... estimate statistics sample 10
>percent' with dbms_stats.gather_schema_stats('x', estimate_percent=>10,
>cascade=>true, degree=>4, method_opt=>''for all indexed columns size 2')
>
>Performace is good against partitioned tables but not for non-partitioned
>tables.
>
>Saw a note in Metalink that its better to do the above with
>'cascade=>false' and then do a gather_index_stats separately.
>
>In my tests, I see that 'analyze' makes the CBO use an index while
>dbms_stats is making the CBO to use a FTS instead.
>
>Have you faced any similar issues?
>
>
>TIA
>Prakash

Wolfgang Breitling
Oracle7, 8, 8i, 9i OCP DBA
Centrex Consulting Corporation
http://www.centrexcc.com

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