Informatica Powercenter Express - All About Lookup Caches

The Integration Service builds a cache in memory when it processes the first row of data in a cached Lookup transformation. The Integration Service creates caches as the source rows enter the Lookup transformation. It allocates memory for the cache based on the amount you configure in the transformation. The Integration Service stores condition values in the index cache and output values in the data cache.

Types of lookup caches

Static Cache

A static cache does not change while the Integration Service processes the lookup. The Integration Service rebuilds a static cache each time it processes the lookup. It looks up values in the cache for each row that comes into the Lookup transformation. When the lookup condition is true, the Integration Service returns a value from the lookup cache. Use a static cache

• If the lookup source does not change while the mapping runs.
• You must use a static cache for an unconnected lookup.
• To increase performance. The Integration Service processes a Lookup transformation with a static cache faster than a lookup transformation with a dynamic cache.

Persistent Cache

A persistent cache does not change each time the Integration Service processes the lookup. The Integration Service saves the lookup cache files and reuses them the next time it processes a Lookup transformation configured to use the cache. Use a persistent cache when the lookup source does not change. You can configure the Lookup transformation to rebuild a persistent lookup cache if necessary.

Dynamic Cache

A dynamic lookup cache changes while the Integration Service processes the lookup. The Integration Service builds a dynamic lookup cache when it processes the first lookup request. When it processes each row, the Integration Service dynamically inserts or updates data in the lookup cache and passes the data to the target. The dynamic cache is synchronized with the target. Use a dynamic cache when you want to update a target based on new and changed records.

Shared Cache

A shared cache can be used by multiple Lookup transformations in the same mapping. Use a shared cache to increase mapping performance. Instead of generating a separate lookup cache for each Lookup transformation, the Integration Service generates one cache.