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Oracle Tips by Burleson |
Chapter 1
Oracle Instance Internals Scripts
Monitoring Waits
Waits occur when Oracle experiences contention
for a specific resource. Tuning should involve monitoring waits,
latches, and locks. We have already looked at latches and locks,
lets look at the third member of this trio, waits. The v$waitstat
DPT is the place to start.
The v$waitstat table is the usual source of
wait information for the average tuner. This table has a very basic
structure:
EXADB>DESC v$waitstat
Name Null?
Type
--------------------------------- --------
------------
CLASS
VARCHAR2(18)
COUNT
NUMBER
TIME
NUMBER
The class column contains the name of the
particular type of wait. The count column gives the total number of
these types of waits that have occurred since the last database
startup. The final column, time, gives the total elapsed time in
centa-seconds (1/100 seconds) that the waits have consumed according
to Oracle’s internal determinations.
A typical select on a large instance may look
like so:
EXADB>SELECT * FROM v$waitstat WHERE count>0;
CLASS COUNT TIME
------------------ ---------- ----------
The above text is
an excerpt from:
Mike
Ault’s Oracle Internals Monitoring & Tuning Scripts
Written by the world's top DBA and author
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Ault brings his expertise to the public with this fantastic
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http://www.rampant-books.com/download_adv_mon_tuning.htm
http://rampant-books.com/book_2003_2_audit.htm
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