This parameter controls the maximum amount of memory PGA which can be used by the queries when WORKAREA_SIZE_POLICY is set to Auto.

The value you can be set in Bytes, kilobytes (K), megabytes (M) or gigabytes (G). The default value is 0

This parameter also has an effect on the execution plans of the cost based optimizer. The optimizer uses the value of the parameter PGA_AGGREGATE_TARGET to derive an estimate

for the minimum and maximum amount of memory which should be available at run-time for each sort, hash-join and bitmap operator in the query. Based on this minimum and maximum value, the

optimizer selects the best plan.