Use a flat file, relational table, or source qualifier for a lookup source. When you create a Lookup transformation, you can create the lookup source from the following locations:
Relational source or target definition in the repository
Flat file source or target definition in the repository
Table or file that the Integration Service and PowerCenter Client machine can connect to
Source qualifier definition in a mapping
The lookup table can be a single table, or you can join multiple tables in the same database using a lookup SQL override. The Integration Service queries the lookup table or an in-memory cache of the table for all incoming rows into the Lookup transformation.
The Integration Service can connect to a lookup table using ODBC or native drivers. Configure native drivers for optimal performance.