Creating a Pass-Through Mapping - Informatica

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:

  • Selects all source rows
  • Inserts all rows into the target

The following figure shows a mapping that the Getting Started Wizard creates when you create a pass-through mapping:

Understanding the 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:

Understanding the Transformations

Steps to Create a Pass-Through Mapping

To create a pass-through mapping:

  1. In the Mapping Designer, click Mappings > Wizards > Getting Started.
  2. Enter a mapping name and select Simple Pass Through, and click Next.
  3. The naming convention for mapping names is m_MappingName.
  4. Select a source definition to use in the mapping.
  5. All available source definitions appear in the Select Source Table list. This list can include shortcuts, flat file, relational, and Application sources.

  6. Enter a name for the mapping target table and click Finish.
  7. 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.

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