Based on the configurations done at lookup transformation/Session Property level, we can have following types of Lookup Caches.
- Un- cached lookup– Here, the lookup transformation does not create the cache. For each record, it goes to the lookup Source, performs the lookup and returns value. So for 10K rows, it will go the Lookup source 10K times to get the related values.
- Cached Lookup– In order to reduce the to and fro communication with the Lookup Source and Informatica Server, we can configure the lookup transformation to create the cache. In this way, the entire data from the Lookup Source is cached and all lookups are performed against the Caches.
Based on the types of the Caches configured, we can have two types of caches, Static and Dynamic.
The Integration Service performs differently based on the type of lookup cache that is configured. The following table compares Lookup transformations with an uncached lookup, a static cache, and a dynamic cache:
Persistent Cache
By default, the Lookup caches are deleted post successful completion of the respective sessions but, we can configure to preserve the caches, to reuse it next time.
Shared Cache
We can share the lookup cache between multiple transformations. We can share an unnamed cache between transformations in the same mapping. We can share a named cache between transformations in the same or different mappings.