histogram tuning factor controls the number of steps Adaptive Server analyzes per histogram for update statistics, update index statistics, update all statistics, and create index.
histogram tuning factor minimizes the resources histograms consume, and only increases resource usage only when it improves optimization. For example, when columns have duplicated values, or data that is not distributed uniformly. Under these circumstances, up to 400 (maximum) histogram steps are used. However, in most cases, Adaptive Server uses the default value (20 in the example above).
For Adaptive Server versions earlier than 15.0.2 ESD #2, the default value for this configuration parameter is 1 (disabled). For Adaptive Server versions 15.0.2 ESD #2 and later, the default for this configuration parameter is 20 (enabled).
See histogram tuning factor in Chapter 5, “Setting Configuration Parameters” in the System Administration Guide: Volume 1.
