The Integration Service builds the cache when it processes the first lookup request. It queries the cache based on the lookup condition for each row that passes into the transformation.

When the lookup condition is true, the Integration Service returns the values from the static lookup cache. When the Integration Service processes a connected Lookup transformation, it returns the values represented by the lookup/output ports. When the Integration Service processes an unconnected Lookup transformation, it returns the value represented by the return port.

When the condition is not true, the Integration Service returns either NULL or default values. When the Integration Service processes a connected Lookup transformation, the Integration Service returns the default value of the output port when the condition is not met. When the Integration Service processes an unconnected Lookup transformation, it returns NULL when the condition is not met.