When you edit a port name in a transformation, by default, the Designer propagates references to that port in the expressions, conditions, and other ports in that transformation. You can also propagate changed attributes throughout the mapping.
The Designer propagates ports, expressions, and conditions based on the following factors:
Understanding Dependency Types
When you propagate port attributes, the Designer can update the following dependencies:
For example, when you change the datatype of a port that is used in a lookup condition, the Designer propagates the datatype change to the other port dependent on the condition.
Propagating Dependencies in a Link Path
When you propagate dependencies in a link path, the Designer updates all the input and input/output ports in its forward link path and all the output and input/output ports in its backward link path. The Designer performs the following updates:
Note:When you propagate a port name, the Designer appends “1” to the port name if a port with the same name exists in the transformation.
In the following mapping, the QTY port in the Joiner transformation links to the QTY port in the Aggregator transformation. The Aggregator transformation references the QTY port in the expressions for TOTAL_QUANTITY and TOTAL_REVENUE:
You make the following changes to the QTY port in the Joiner transformation:
When you propagate forward the attributes, the Designer updates the following dependencies in the Aggregator transformation:
Propagating Implicit Dependencies
You can propagate datatype, precision, scale, and description to ports with implicit dependencies. When you click Options in the Propagate Ports dialog box, you can choose to parse conditions and expressions to identify the implicit dependencies of the propagated port. All ports with implicit dependencies are output or input/output ports.
When you include conditions the Designer updates the following dependencies:
When you include expressions, the Designer updates the following dependencies:
The Designer does not propagate to implicit dependencies within the same transformation. You must propagate the changed attributes from another transformation. For example, when you change the datatype of a port that is used in a lookup condition and propagate that change from the Lookup transformation, the Designer does not propagate the change to the other port dependent on the condition in the same Lookup transformation.
You have the following mapping:
The MANUFACTURER_ID port in the Aggregator transformation links to the IN_MANUFACTURER_ID port in the Lookup transformation. The Lookup transformation uses the following lookup condition:MANUFACTURER_ID = IN_MANUFACTURER_ID
You change the datatype of the MANUFACTURER_ID port from integer to decimal in the Aggregator transformation. You choose to parse conditions to infer dependencies, and then propagate the datatype change.
The Designer performs the following tasks:
Propagated Attributes by Transformation
The following table describes the dependencies and attributes the Designer propagates for each transformation:
The Designer does not propagate changes to the following mapping objects:
Rules and Guidelines for Propagating Ports and Attributes
Use the following rules and guidelines when you propagate port attributes:
For example, you have the following expression in an Expression transformation:Item_desc_out = Substr(ITEM_NAME, 0, 6) || Substr(ITEM_DESC, 0, 6)
The precision of Item_desc_out is 12, ITEM_NAME is 10, and ITEM_DESC is 10. You change the precision of ITEM_DESC to 15. You select parse expressions to infer dependencies and propagate the port attributes of ITEM_NAME and ITEM_DESC. The Designer does not update the precision of the Item_desc_out port in the Expression transformation since the ITEM_NAME and ITEM_DESC ports have different precisions.
Steps to Propagate Port Attributes
Complete the following steps to propagate port attributes.
To propagate port attributes:
The Designer displays the Propagate Port Attributes dialog box.
After you open the Propagate Port Attributes dialog box, you can select another port and propagate its attributes.
The following table describes the options on the Propagate Port Attributes dialog box:
The Designer displays the links to the affected ports in green and the unaffected ports in red.
When you propagate port attributes, the Output window displays the propagated attributes and the affected ports.
Using The Designer
Working With Sources
Working With Flat Files
Working With Targets
Mapping Parameters And Variables
Working With User-defined Functions
Using The Debugger
Viewing Data Lineage
Managing Business Components
Creating Cubes And Dimensions
Using The Mapping Wizards
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