The Update Strategy transformation in Informatica PowerCenter is crucial for controlling how the Integration Service writes data to target tables. It allows you to specify whether a row should be inserted, updated, deleted, or rejected. Here's a breakdown:
Purpose :
- The Update Strategy transformation enables you to direct the Integration Service to perform different actions on target rows based on conditions within your data.
- This is essential for maintaining data integrity and accurately reflecting changes in your source data.
Key Options :
The Update Strategy transformation uses specific expressions to indicate the desired action for each row. These expressions are typically placed within an expression transformation that is then linked to the update strategy transformation. The main options are:
- DD_INSERT:
- Marks the row for insertion into the target table.
- Used when you want to add new rows to the target.
- DD_UPDATE:
- Marks the row for updating in the target table.
- Used when you want to modify existing rows in the target.
- DD_DELETE:
- Marks the row for deletion from the target table.
- Used when you want to remove rows from the target.
- DD_REJECT:
- Marks the row for rejection.
- Used when you want to prevent a row from being written to the target, often due to data quality issues.
How it Works :
- Data Flow:
- Data flows through the mapping, and transformation logic is applied.
- Expression Evaluation:
- Within an Expression transformation (or sometimes within the update strategy transformation itself), an expression is evaluated for each row.
- This expression determines which DD_ operation should be applied.
- Update Strategy Application:
- The Update Strategy transformation reads the DD_ code and instructs the Integration Service to perform the corresponding action on the target table.
- Target Update:
- The Integration service then carries out the actions on the target database.
Importance :
- The Update Strategy transformation provides granular control over target data manipulation.
- It is essential for implementing complex data integration scenarios, such as incremental loading and data synchronization.
- It allows for the proper implementation of SCD's(Slowly Changing Dimensions).
By effectively using the Update Strategy transformation, you can ensure that your target data is accurate and up-to-date.
