Impact Analysis on Source & Target Definition Changes

Changes to Source and Target definition will impact the current state of the Informatica mapping and below lists the possible changes at Source and the Target with impact.
Updating Source Definitions: When we update a source definition, the Designer propagates the changes to all mappings using that source. Some changes to source definitions can invalidate mappings.
Below table describes how the mappings get impacted when the source definition is edited:

Modification	Result  of the source after modifying the source definition
Add a column.	Mappings are not invalidated.
Change a column Data type.	Mappings may be invalidated. If the column is connected to an input port that uses a Data type incompatible with the new one, the mapping is invalidated.
Change a column name.	Mapping may be invalidated. If you change the column name for a column you just added, the mapping remains valid. If you change the column name for an existing column, the mapping is invalidated.
Delete a column.	Mappings can be invalidated if the mapping uses values from the deleted column.

Adding a new column in the existing source definition:

• When we add a new column to a source in the Source Analyzer, all mappings using the source definition remain valid.
• However, when we add a new column and change some of its properties, the Designer invalidates mappings using the source definition.
• We can change the following properties for a newly added source column without invalidating a mapping: 

1. Name
2. Data type
3. Format
4. Usage
5. Redefines
6. Occurs
7. Key type

If the changes invalidate the mapping, we must open and edit the mapping. Then click Repository > Save to save the changes to the repository. If the invalidated mapping is used in a session, we must validate the session.
Updating Target Definitions:
When we change a target definition, the Designer propagates the changes to any mapping using that target. Some changes to target definitions can invalidate mappings.
The following table describes how the mappings get impacted when we edit target definitions:

Modification	Result  of the source after modifying the target definition
Add a column.	Mapping not invalidated.
Change a column Data type.	Mapping may be invalidated. If the column is connected to an input port that uses a Data type that is incompatible with the new one (for example, Decimal to Date), the mapping is invalid.
Change a column name.	Mapping may be invalidated. If you change the column name for a column you just added, the mapping remains valid. If you change the column name for an existing column, the mapping is invalidated.
Delete a column.	Mapping may be invalidated if the mapping uses values from the deleted column.
Change the target definition type.	Mapping not invalidated.

Adding a new column in the existing target definition:

• When we add a new column to a target in the Target Designer, all mappings using the target definition remain valid.
• However, when you add a new column and change some of its properties, the Designer invalidates mappings using the target definition.
• We can change the following properties for a newly added target column without invalidating a mapping:

1. Name
2. Data type
3. Format
If the changes invalidate the mapping, validate the mapping and any session using the mapping. We can validate objects from the Query Results or View Dependencies window or from the Repository Navigator. We can validate multiple objects from these locations without opening them in the workspace. If we cannot validate the mapping or session from one of these locations, open the object in the workspace and edit it.
Re-importing a Relational Target Definition:
If a target table changes, such as when we change a column data type, we can edit the definition or we can re-import the target definition. When we re-import the target, we can either replace the existing target definition or rename the new target definition to avoid a naming conflict with the existing target definition.
To re-import a target definition:

• In the Target Designer, follow the same steps to import the target definition, and select the    Target to import. The Designer notifies us that a target definition with that name already exists in the repository. If we have multiple tables to import and replace, select apply to All Tables.
• Click Rename, Replace, Skip, or Compare.
• If we click Rename, enter the name of the target definition and click OK.
• If we have a relational target definition and click Replace, specify whether we want to retain primary key-foreign key information and target descriptions

The following table describes the options available in the Table Exists dialog box when re-importing and replacing a relational target definition:

Option	Description
Apply to all Tables	Select this option to apply rename, replaces, or skips all tables in the folder.
Retain User-Defined PK-FK Relationships	Select this option to keep the primary key-foreign key relationships in the target definition being replaced. This option is disabled when the target definition is non-relational.
Retain User-Defined Descriptions	Select this option to retain the target description and column and port descriptions of the target definition being replaced.