At IBM IOD last week, I attended a session where the IBM presenter called it
Index Selectivity - I was flattered because the speaker's explanation was
almost verbatim from the DB2 Magazine blog post:
http://www.db2mag.com/blog/main/archives/2007/06/db2_luw_perform_1.html
and you can learn more here too:
http://www.database-brothers.com/brother-eagle/advice/db2dbiref.php
I've called this metric Index Read Efficiency (or IREF for short) because
the measurement reflects the quality of indexes that are present, if any.
IREF can be computed at the Database level to assess the overall index
quality for a database, or for individual Statements to assess the quality
of indexes available to a given statement.
Cheers,
Scott
PS - While you're at it, download www.Brother-Eagle.com Standard Edition
(free) and automatically measure Index Read Efficiency and 23 other
important database metrics.
-----Original Message-----
From: Jagdish Singh Rawat NCS
[mailto:db2udbdba-ezmlmshield-x10584837.[Email address protected]
Sent: Tuesday, October 23, 2007 12:01 AM
To: LazyDBA Discussion
Subject: RE: "Index Read Efficiency"
Hi Bhagwati,
IRE can be calculated by
IRE = Rows read / Rows Selected (Fetched)
Thanks
Jagdish S. Rawat
IBM Certified Advance DB2DBA
NCS Pte. Ltd.
5 Ang Mo Kio St 62, NCS Hub
Singapore - 569141
Ph.# +65-65565870(Direct) +65-65568000 Ext. # 5870
HP.# +65-96425135
Fax# +65-64830495
-----Original Message-----
From: Bhagwati Goenka
[mailto:db2udbdba-ezmlmshield-x30655245.[Email address protected]
Sent: Saturday, October 20, 2007 11:08 PM
To: LazyDBA Discussion
Subject: "Index Read Efficiency"
Has anyone ever heard of "Index Read Efficiency"? Is this a standard,
accepted way of measuring database efficiency? I can't seem to find
anything about this except at some company's (DBI) website. I looked at
IBM literature, but couldn't find anything.
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