A mapping that contains an unconnected Lookup transformation receives input values from the result of a :LKP expression in another transformation, such as an Aggregator transformation, Expression transformation, or Update Strategy transformation. The Integration Service queries the lookup source or cache based on the lookup ports and condition in the Lookup transformation. The Integration Service returns a value through the return port of the Lookup transformation. The Integration Service passes the return value to the port that contains the :LKP expression.

The following mapping shows a mapping that contains an unconnected Lookup transformation and the Expression transformation that processes the lookup expression:

Perform the following tasks to configure an unconnected lookup transformation:

Create an input port in the Lookup transformation for each argument in the :LKP expression. You can create a different port for each condition, or use the same input port in more than one condition.
In this case, create a lookup condition that compares the DEPTID_EMP in the source with the DEPTID in the target. Retrieve the DEPTNAME for each employee in the source with respect to the department name in the target. Create an input port (DEPTID_PARAM) with the data type String (10,0) to match the DEPTID_PARAM lookup port.
After you configure the ports, define a lookup condition to compare transformation input values with values in the lookup source or cache. To increase performance, add conditions with an equal sign first. In this case, add the following lookup condition:
DEPTID = DEPTID_PARAM
Designate one lookup/output port as a return port. In this case, you can define the DEPTNAME port as the return port.
The following image shows a return port in a Lookup transformation:

Do not configure the lookup policy to use all values on multiple matches for an unconnected Lookup transformation.
Supply input values for an unconnected Lookup transformation from a :LKP expression in another transformation. The arguments are local input ports that match the Lookup transformation input ports used in the lookup condition. In this case, add the following :LKP expression in the Expression transformation:
:LKP.LKPTRANS(DEPTID_EMP)