By default, the Integration Service uses a non-persistent cache when you enable lookup caching in a Lookup transformation. The Integration Service deletes the cache files when the mapping completes. The next time you run the mapping, the Integration Service builds the memory cache from the lookup source.

If you configure the Lookup transformation to use a persistent lookup cache, the Integration Service saves and reuses cache files for multiple runs of the mapping. A persistent cache eliminates the time required to read the lookup table and rebuild the lookup cache.

The first time the Integration Service runs a mapping with a persistent lookup cache, the Integration Service saves the cache files to disk. The next time the Integration Service runs the mapping, it builds the memory cache from the cache files.

You can configure the Integration Service to rebuild a persistent lookup cache if the original lookup source changes. When you rebuild a cache, the Integration Service creates new cache files and writes a message to the Integration Service log.