Into the Shared Pool - An In Depth Look at Tuning the Shared Pool (Part 2)
Oracle Tips by Mike Ault
Monitoring Library and Data
The output from the script in Figure 11 is
shown in Figure 12.
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Time: 02:59 PM DD Cache Hit
Figure 12: Example Output From Data Dictionary
The ratio reported from the script in Figure 11
should always be less than 1. The ratio corresponds to the number of
times out of 100 that the database engine sought something from the
cache and missed. A dictionary cache miss is more expensive than a
data block buffer miss so if your ratio gets near 1 increase the
size of the shared pool since the internal algorithm isn't
allocating enough memory to the data dictionary caches.
Guideline 8: In any shared pool, if the overall
data dictionary cache miss ratio exceeds 1 percent, increase the
size of the shared pool.
For more information on this topic, I recommend Don
Burleson's latest book "Oracle
Tuning: The Definitive Reference".
You can buy it direct from the publisher for 50%-off and get
instant access to the code depot of Oracle tuning scripts:
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