Adaptive Optimizer Features

Adaptive Dynamic Sampling and the Result Cache: RC Latch

After we migrated one of our instances from Oracle 11.2.0.4 to 12.1.0.2 we ran into some serious latch contention that basically took down the instance.  From online research, and discussion with other DBAs I don’t think we are the only customer that has run into this problem, so I wanted to share my investigation and …

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Incorrect Cardinality Adjustment caused by Dynamic Statistics

During migration testing to Oracle 12, one of our teams complained about regression of a particular query. Drilling into what was going on identified some a problem with Adaptive Dynamic Sampling, and certainly not the first one we have encountered. I will detail the steps to reproduce, and my understanding of what is going on. …

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