Re: How do you un-analyze tables?

1. analyse <object> delete statistics;
2. There are many many reasons why CBO might make the wrong decisions. these include , but are not limited to
   1. too small or unrepresentative a sample,
   2. skewed data distributions,
   3. poorly chosen init.ora parameters (for example db_multi_block_read_count)
   4. poor indexing of the data.

You should also be aware that the rules used for RULE optimisation do not take any account of many of the nice new features introduced in Oracle 8 & 8i. for example I don't believe you'll ever get Oracle to use a materialized view under RULE.

HTH

--
Niall Litchfield
Oracle DBA
Audit Commission UK
"George Barbour" <george.barbour_at_gecm.com> wrote in message
news:3b3b2c17$1_at_pull.gecm.com...


> Hi all,

> Oracle 8.1.5.

> Sun Solaris Unix 2.8.

> The situation, I have many Oracle Discoverer queries against the database.

>  Some queries run as RULE and some ran as COST.

> I analyzed the objects, mistake! Now all of the queries run as COST. The

> difference in run time is spectacular.

> Rule based = 17.9 secs.

> Cost based = 388 mins.

>

> 1)  How to I un-analyze objects, to get back to where I was before?

> 2)  Why doesn't the system use the blatantly faster optimisation mode?

>

> George Barbour.

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