Penrose uses 2-level cache: source cache and entry cache. The source cache caches the data read from the datasources. The entry cache caches the entries generated by the mappings.

Penrose comes with two types of cache:

• No Cache. This is recommended for real-time mapping (default).
• In-Memory Cache. This is recommended for databases that are small or rarely change.
• Persistent Cache. This is recommended for databases that are large or often change.