option increases the use of dictionary values for masking and reduces duplicate dictionary values in the target.
If you perform substitution masking or custom substitution masking, you can choose to optimize the dictionary usage. The workflow uses some values from the selected dictionary to mask source data. These dictionary values might be used for multiple entries so that all source data is masked in the target. The chances of using duplicate dictionary values reduces if you optimize dictionary usage. To optimize dictionary output, you must configure the masking rule for repeatable output.