Dynamic Performance (V$) Views, 132 of 238

V$PGA_TARGET_ADVICE_HISTOGRAM

V$PGA_TARGET_ADVICE_HISTOGRAM predicts how statistics displayed by the V$SQL_WORKAREA_HISTOGRAM dynamic view would be impacted if the value of the PGA_AGGREGATE_TARGET parameter is changed. This prediction is performed for various values of the PGA_AGGREGATE_TARGET parameter, selected around its current value. The advice statistic is generated by simulating the past workload run by the instance.

The content of the view is empty if PGA_AGGREGATE_TARGET is not set. In addition, the content of this view is not updated when the STATISTICS_LEVEL initialization parameter is set to BASIC. Base statistics for this view are reset at instance startup or when the value of the PGA_AGGREGATE_TARGET initialization parameter is dynamically modified.

Column	Datatype	Description
`PGA_TARGET_FOR_ESTIMATE`	`NUMBER`	Value of `PGA_AGGREGATE_TARGET` for this prediction (in bytes)
`PGA_TARGET_FACTOR`	`NUMBER`	`PGA_TARGET_FOR_ESTIMATE` / the current value of the `PGA_AGGREGATE_TARGET` parameter
`ADVICE_STATUS`	`VARCHAR2(3)`	Indicates whether the advice is enabled (`ON`) or disabled (`OFF`) depending on the value of the `STATISTICS_LEVEL` parameter
`LOW_OPTIMAL_SIZE`	`NUMBER`	Lower bound for the optimal memory requirement of work areas included in this row (in bytes)
`HIGH_OPTIMAL_SIZE`	`NUMBER`	Upper bound for the optimal memory requirement of work areas included in this row (in bytes)
`ESTD_OPTIMAL_EXECUTIONS`	`NUMBER`	Number of work areas with an optimal memory requirement comprised between `LOW_OPTIMAL_SIZE` and `HIGH_OPTIMAL_SIZE` which are predicted to run optimal given a value of `PGA_AGGREGATE_TARGET` equal to `PGA_TARGET_FOR_ESTIMATE`
`ESTD_ONEPASS_EXECUTIONS`	`NUMBER`	Number of work areas with an optimal memory requirement comprised between `LOW_OPTIMAL_SIZE` and `HIGH_OPTIMAL_SIZE` which are predicted to run one-pass given a value of `PGA_AGGREGATE_TARGET` equal to `PGA_TARGET_FOR_ESTIMATE`
`ESTD_MULTIPASSES_EXECUTIONS`	`NUMBER`	Number of work areas with an optimal memory requirement comprised between `LOW_OPTIMAL_SIZE` and `HIGH_OPTIMAL_SIZE` which are predicted to run multi-pass given a value of `PGA_AGGREGATE_TARGET` equal to `PGA_TARGET_FOR_ESTIMATE`
`ESTD_TOTAL_EXECUTIONS`	`NUMBER`	Sum of `ESTD_OPTIMAL_EXECUTIONS`, `ESTD_ONEPASS_EXECUTIONS`, and `ESTD_MULTIPASSES_EXECUTIONS`
`IGNORED_WORKAREAS_COUNT`	`NUMBER`	Number of work areas with optimal memory requirement between `LOW_OPTIMAL_SIZE` and `HIGH_OPTIMAL_SIZE` ignored in the advice generation due to memory and CPU constraints

See Also:

Oracle9i Database Performance Tuning Guide and Reference for information on tuning the PGA_AGGREGATE_TARGET initialization parameter using the PGA advice views