Hello,

I'd like to understand about Statistic...

Well, my doubts are :
1) I need run this sequence LOW MEDIUM AND HIGH statistic for the same table ??

2) What the difference between LOW, MEDIUM AND HIGH ?

3) IF i don't know the index from one table, and I run ex:

UPDATE STATISTICS HIGH FOR TABLE consumo_teorico DISTRIBUTIONS ONLY;

I got the same performance if I knew the index ???

The manual (Performance Guide) say a lot things about guide lines to update statistics and have some articles on IBM site about this.
But, the basic guide lines are:
Medium and big tables:
- update statistics HIGH in head columns (first columns) from any index
- update statistics medium to another's columns where is part of a index
- update statistics medium to columns where is used to filter.
to small tables:
- update statistics high , all columns

Execute update statistics more frequently on tables where the data are modified frequently.
Example:
if you have a table with all move of a stock system , and all days have delete/inserts/updates on this table, consider executing the update statistics at least 1 time for week.


Link to All PDFs manuals , all versions, free of charge:
http://www-306.ibm.com/software/data...ubs/library/#3

Creating Data Distributions
http://publib.boulder.ibm.com/infoce...13query1-20817

Updating Statistics on Very Large Databases
http://publib.boulder.ibm.com/infoce...69%73%74%22%20

Updating Statistics for Join Columns
http://publib.boulder.ibm.com/infoce...69%73%74%22%20

Somes TechNotes from IBM Support Site:
http://www-1.ibm.com/support/search.....y=0&ibm-go=Go

I forgot..

include on basic guide lines:
First : - update statistics LOW to all tables.

I was thinking about u said..


Well, My big table has around 4 Million lines and Small tables 120 thousands lines..


My database isn`t 24 / 7, so I can put in crontab to run tonight...

If I put:

Medium and big tables: (4 Million)
- update statistics medium (all columns)

Hight to small tables: ( < 120.000)
- update statistics high (all columns )

Can I got best performance using that statistics ?

What do u think..

This is very hard to say, this can variable in each environment.

but, my personal opinion, this is almost ok, missing only the update statistics low for all tables first , and the update statistics HIGH to all head index columns
Tip, when you put the update statistics , if no user are using the database, use the SET PDQPRIORITY 100 , and review your configurations of PDQ on your ONCONFIG. This will boost the time execution from your update statistics