Table statistics - DB2 Database

Lyn Duong

Hi,

I have a job that performs a runstats on tables in my database (db2 V8
on AIX) and the syntax is

db2 runstats on table schema.tabname with distribution and detailed
indexes all.

when I look at the statistics in syscat.indexes table, the values for
AVERAGE_SEQUENCE_FETCH_PAGES,AVERAGE_RANDOM_FETCH_ PAGES etc (for
prefetch statistics) is -1 which means unknown. Why is this so and
what must be turned on in order to obtain these statistics for
analysis

Thanks
Lyn

Nov 12 '05 #1

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Mark A

"Lyn Duong" <ly**@tablimited.com.au> wrote in message
news:8d**************************@posting.google.c om...

Hi,

I have a job that performs a runstats on tables in my database (db2 V8
on AIX) and the syntax is

db2 runstats on table schema.tabname with distribution and detailed
indexes all.

when I look at the statistics in syscat.indexes table, the values for
AVERAGE_SEQUENCE_FETCH_PAGES,AVERAGE_RANDOM_FETCH_ PAGES etc (for
prefetch statistics) is -1 which means unknown. Why is this so and
what must be turned on in order to obtain these statistics for
analysis

Thanks
Lyn

May be because the index is too small for those stats to be meaningful so
DB2 does not collect them.

Nov 12 '05 #2

PM $pm3iinc-nospam$

I just came across this info the other day. (lucky you)

http://publib.boulder.ibm.com/infoce...help/index.jsp
search : AVERAGE_SEQUENCE_FETCH_PAGES
See sysstat.indexes catalog view
1.. When using DMS table spaces, this statistic cannot be computed.
2.. Prefetch statistics are not gathered during a LOAD...STATISTICS YES,
or a CREATE INDEX...COLLECT STATISTICS operation, or when the database
configuration parameter seqdetect is turned off.
PM

"Lyn Duong" <ly**@tablimited.com.au> a écrit dans le message de
news:8d**************************@posting.google.c om...

Hi,

I have a job that performs a runstats on tables in my database (db2 V8
on AIX) and the syntax is

db2 runstats on table schema.tabname with distribution and detailed
indexes all.

when I look at the statistics in syscat.indexes table, the values for
AVERAGE_SEQUENCE_FETCH_PAGES,AVERAGE_RANDOM_FETCH_ PAGES etc (for
prefetch statistics) is -1 which means unknown. Why is this so and
what must be turned on in order to obtain these statistics for
analysis

Thanks
Lyn

Nov 12 '05 #3

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