When you run a mapping to analyze identity information, the Match transformation generates an index that stores the alternative versions of the identities in the data set. By default, the Match transformation writes the index data to temporary files. You can configure the transformation to save the index data to database tables.
The index tables that you generate represent a data store that you can reuse in subsequent mappings. You can compare the index tables to a data source, and you can optionally update the index tables with index data from the data source. Because the transformation does not regenerate the index tables, the subsequent mappings run faster. Additionally, the index tables can represent a trusted data store of identity data.