The Informatica server builds a cache in memory when it processes the first row of a data in a cached look up transformation. It allocates memory for the cache based on the amount you configure in the transformation or session properties. The Informatica server stores condition values in the index cache and output values in the data cache.
The result of the Lookup query and processing is the same, whether or not you cache the lookup source. However, using a lookup cache can increase session performance. You can optimize performance by caching the lookup source when the source is large.
If the lookup does not change between sessions, you can configure the transformation to use a persistent lookup cache. When you run the session, the Integration Service rebuilds the persistent cache if any cache file is missing or invalid.
The Integration Service creates the following caches for the Lookup transformation:
Data cache. For a connected Lookup transformation, stores data for the connected output ports, not including ports used in the lookup condition. For an unconnected Lookup transformation, stores data from the return port.
Index cache. Stores data for the columns used in the lookup condition.
Types of lookup caches?
1. Static cache
2. Dynamic cache
3. Persistence cache
5. Shared cache