Inside adaptive cursor sharing

Oracle has improved cursor_sharing several times over the years.  Remember, adaptive cursor sharing is only deployed in rare cases where a skewed column distribution (as noted by the histogram), indicates that a different execution plan would be faster.  For example, a query with a popular bind variable value would be best served with a full table scan while an unpopular bind variable value would benefit from an index access plan.

But remember, this is a rare occurrence in many systems.

In my experience at BC, about 80% of shops have uniformly distributed data. Large tables remain large, and the distribution of values within a column remain unchanged.

On the other hand, we have roughly 20% of databases that experience highly volatile data loads, where tables are small on one day and huge the next, or cases where the is a "difference that makes a difference". In these databases, huge changes in the tables data (usually associated with high DML) changes the distribution of data values, necessitating a re-analysis of column histograms.

Read more about 11g adaptive cursor sharing:


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How do I do that in Oracle?

Explore this series for a collection of tips that explain in detail how to perform specific tasks in Oracle related to database administration. Consisting of expert advice from top Oracle gurus, these how-tos provide step-by-step instructions to guide you through database administration processes related to installation and upgrades, backup and recovery and other Oracle basics.,289483,sid41_gci1264060,00.html?Offer=ORburl0206