You must enable the Lookup transformation to perform a conditional dynamic cache lookup before you can create a conditional expression.
Use the following steps to configure a conditional dynamic cache lookup:
Create a dynamic Lookup transformation in the Transformation Developer.
Click the Properties tab.
Enable Lookup Caching and Dynamic Lookup Cache properties.
To access the Expression Editor, click the Go button for the Update Dynamic Cache Condition property.
Define an expression condition. You can select input ports, lookup ports, and functions for the expression.
Click Validate to verify that the expression is valid.
If you do not validate an expression, the Designer validates it when you close the Expression Editor. If the expression is not valid, the Designer displays a warning.