The pass-through mapping inserts all source rows. Use the pass-through mapping to load tables when you do not need to keep historical data in the target table. If source rows already exist in the target, truncate or drop the existing target before running the workflow. In the pass-through mapping, all rows are current.
You might use the pass-through mapping to load a fact or dimension table if the table remains static for a period of time, and then changes dramatically.
For example, you might have a vendor dimension table that remains the same for a year. At the end of the year, you reload the table to reflect new vendor contracts and contact information. If this information changes dramatically and you do not want to keep historical information, you can drop the existing dimension table and use the pass-through mapping to reload the entire table. If the information changes only incrementally, you might prefer to update the existing table using the Type 1 Dimension mapping created by the Slowly Changing Dimensions Wizard.
Understanding the Mapping
The pass-through mapping performs the following tasks:
The following figure shows a mapping that the Getting Started Wizard creates when you create a pass-through mapping:
A single data flow passes from a source definition, through a source qualifier and an Expression transformation, to the target. By default, the Expression transformation passes data directly to the target without changes.
Understanding the Transformations
The following table describes the function of each transformation in the pass-through mapping:
Steps to Create a Pass-Through Mapping
To create a pass-through mapping:
All available source definitions appear in the Select Source Table list. This list can include shortcuts, flat file, relational, and Application sources.
The new mapping appears in the workspace. The naming convention for target definitions is T_TARGET_NAME.
Make necessary edits to the mapping.
Create the target table in the target database before running a workflow.
Customizing the Mapping
After the wizard creates the mapping, you can configure the Expression transformation, EXP_TransformData. You can also add any other transformations to customize the mapping.
If you want data to pass directly from source to target without any other transformations, delete the Expression transformation. You can optimize performance for pass-through mappings by connecting the source qualifier directly to the target.
Configuring a Pass-Through Session
The pass-through mapping inserts source rows into the target. To prevent primary key errors from duplicate rows, drop or truncate the target table before running the workflow. Use the truncate target table option in the session properties, or use a pre-session shell command to perform this task automatically.
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
All rights reserved © 2018 Wisdom IT Services India Pvt. Ltd
Wisdomjobs.com is one of the best job search sites in India.