The Integration Service can build lookup caches for connected Lookup transformations in the following ways:
. The Integration Service builds lookup caches sequentially. The Integration Service builds the cache in memory when it processes the first row of the data in a cached lookup transformation.
. The Integration Service builds lookup caches concurrently. It does not need to wait for data to reach the Lookup transformation.
The Integration Service builds caches for unconnected Lookup transformations sequentially regardless of how you configure cache building. If you configure the session to build concurrent caches for an unconnected Lookup transformation, the Integration Service ignores this setting and builds unconnected Lookup transformation caches sequentially.