Use the following rules and guidelines when you configure the Integration Service to push an unconnected Lookup transformation to a database:
The database might perform slower than the Integration Service if the session contains multiple unconnected lookups. The generated SQL might be complex because the Integration Service creates an outer join each time it invokes an unconnected lookup. Test the session with and without pushdown optimization to determine which session has better performance.
Configure the session for pushdown optimization with a view.
The Integration Service processes the unconnected Lookup transformation if any of the following conditions are true:
The lookup connection is not pushdown compatible with the source connection.
You configure target-side pushdown optimization.
The transformation is downstream from an Aggregator transformation.
The transformation is active and looks up from a Netezza database.