AW: members in a file

["BirgittaHauser" <Hauser@xxxxxxxxxxxxxxx>]

Hi,

> > What happens if you stop and start collection of SQL Statistics? 

Statistics are used by the SQE optimizer to determine the optimal index. 
The statistics contain information about how much rows in a table meet the
available key values in an index.
For example if you want to select all order from a specified client and
around 80% of all orders are from this client, the optimizer will favor a
table scan instead of using an index. If an other client will be selected an
index can be used.
Statistics are collected by a job QDBFSTCCOL running on the lowest level. If
you stop statistics collection the SQE optimizer may not find the best
access method, because the statistics do not reflect the current level and
eventually estimates must be used. 
When restarting the statistics collection it will take some time until the
statistics are completely actualized.

BTW the CQE optimizer can only use estimates. For example for an = specified
in a where condition 10% of the rows in a table are expected/estimated.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok)
"What is worse than training your staff and losing them?  Not training them
and keeping them!"

-----Ursprüngliche Nachricht-----
Von: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] Im Auftrag von Evan Harris
Gesendet: Friday, December 28, 2007 22:51
An: 'Midrange Systems Technical Discussion'
Betreff: RE: members in a file


What happens if you stop and start collection of SQL Statistics ? I dimly
recall needing to do this at about V5R2 to make certain things happen

Regards
Evan Harris

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Paul Nelson
Sent: Saturday, 29 December 2007 4:37 a.m.
To: 'Midrange Systems Technical Discussion'
Subject: RE: members in a file

Probably. WRKOBJ *ALL/SYSPSTAT  came up empty.


Paul Nelson
Cell 708-670-6978
Office 512-392-2577
nelsonp@xxxxxxxxxxxxx


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Friday, December 28, 2007 9:29 AM
To: Midrange Systems Technical Discussion
Subject: RE: members in a file

It's in library QSYS2.  As of some release QSYS2 is in QSYSLIBL.  Perhaps 
the term "partitions" arrived later, like, at some SUPPORTED release.  ;-)

Rob Berendt