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 LDAP entries generated by the mappings.
Each source and entry mapping has its own cache and it's configured separately. See Sources and Entries. Currently you can configure the cache size and expiration. The cache will be invalidated when it's expired or an update operation is performed against it.
You can disable cache entirely by setting the Source and Entry cache expiration to 0. In this case no data will be cached, all requests will be forwarded directly to the datasource.