The Match Frequency stage generates frequency distributions, which are needed for input to the matching process. Distributions are generated independently from the matching job.
The stage takes input from a database, file, or processing stage, and generates the frequency distribution of values for columns in the input data.
You use frequency information along with input data when you run the One-source Match or Two-source Match stages. Having the frequency information generated separately means you can reuse it as necessary, and you do not have to generate it whenever you run a one-source or two-source matching job.