Understanding Buffer Pool Performance and Tuning in DB2 UDB v8.1
Understanding Buffer Pool Performance and Tuning in DB2 UDB v8.1
Understanding Buffer Pool Performance and Tuning in DB2 UDB v8.1
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Logical vs. Physical IO<br />
� Data Hit Rate<br />
– Includes ALL data reads by buffer pool<br />
<strong>Buffer</strong>pool<br />
DHR<br />
=<br />
⎛<br />
⎜<br />
⎝<br />
bp.<br />
data.<br />
logical . reads<br />
bp.<br />
data.<br />
logical . reads + bp.<br />
data.<br />
physical . reads<br />
� Low values = more physical IO<br />
� High values = more logical IO<br />
� 85 – 90% is a good start<strong>in</strong>g po<strong>in</strong>t<br />
⎞<br />
⎟*<br />
100<br />
⎠
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