January 2012
Intermediate to advanced
542 pages
11h 28m
English
Content preview from Oracle Database 11gR2 Performance Tuning CookbookBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Collecting statistics
To work well, the optimizer relies on information about both—the data structures involved in the query and the data contained in them; the latter information is provided by statistics.
In this recipe, we will see how to collect statistics on database objects and see its effects on the optimizer's performance.
How to do it...
The following steps will show how to collect statistics on database objects:
- Connect to
SHschema:CONNECT sh@TESTDB/sh - Collect statistics on the
CUSTOMERStable:EXEC DBMS_STATS.GATHER_TABLE_STATS (OWNNAME => 'SH', - TABNAME => 'CUSTOMERS', - ESTIMATE_PERCENT => 20, BLOCK_SAMPLE => TRUE, - CASCADE => TRUE, DEGREE => 4);
- Query for some statistic data collected in the previous step:
SET PAGESIZE 100 SET ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.