Howdy,
I must not know what I'm doing here. I ran a Statspack report for 2
different periods of time, each an hour long. In the first case, my instance
efficiency percentages look pretty bad. They look like this:
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait Ratio: 100.00
Buffer Hit Ratio: 20.00
Library Hit Ratio: 93.04
Redo NoWait Ratio: 100.00
In-memory Sort Ratio: 99.83
Soft Parse Ratio: 85.75
Latch Hit Ratio: 100.00
In the second case, the percentages look much better:
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait Ratio: 100.00
Buffer Hit Ratio: 85.98
Library Hit Ratio: 99.94
Redo NoWait Ratio: 99.99
In-memory Sort Ratio: 99.99
Soft Parse Ratio: 99.84
Latch Hit Ratio: 99.98
However, when I look at the top 5 wait events, the top 2 in the first case
look like this:
Event Waits Time (cs) Wt
Time
-------------------------------------------- ------------ ------------
-------
db file scattered read 31,734 22,189
91.97
db file sequential read 10,096 1,478
6.13
In the second case, they look like this:
Event Waits Time (cs) Wt
Time
-------------------------------------------- ------------ ------------
-------
db file scattered read 163,392 121,906
86.61
db file sequential read 1,421,550 14,968
10.63
There are far more waits and more time spent waiting in the second case. Yet
my hit ratios are much better the second time. Am I comparing apples and
oranges here? What should I be more concerned about?
Bill Carle
AT&T
Database Administrator
816-995-3922
[EMAIL PROTECTED]
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--
Author: Carle, William T (Bill), NLCIO
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