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Sunday, 26 January 2014

Pushdown optimization and types in Informatica


By on 06:14:00


The types of pushdown optimization:

Source-side pushdown optimization. The Integration Service pushes as much transformation logic as possible to the source database.

Target-side pushdown optimization. The Integration Service pushes as much transformation logic as possible to the target database.

Full pushdown optimization. The Integration Service attempts to push all transformation logic to the target database. If the Integration Service cannot push all transformation logic to the database, it performs both source-side and target-side pushdown optimization.

Running Source-Side Pushdown Optimization Sessions

When you run a session configured for source-side pushdown optimization, the Integration Service analyzes the mapping from the source to the target or until it reaches a downstream transformation it cannot push to the source database.

The Integration Service generates and executes a SELECT statement based on the transformation logic for each transformation it can push to the database. Then, it reads the results of this SQL query and processes the remaining transformations.

Running Target-Side Pushdown Optimization Sessions

When you run a session configured for target-side pushdown optimization, the Integration Service analyzes the mapping from the target to the source or until it reaches an upstream transformation it cannot push to the target database. It generates an INSERT, DELETE, or UPDATE statement based on the transformation logic for each transformation it can push to the target database. The Integration Service processes the transformation logic up to the point that it can push the transformation logic to the database. Then, it executes the generated SQL on the target database.

Running Full Pushdown Optimization Sessions

To use full pushdown optimization, the source and target databases must be in the same relational database management system. When you run a session configured for full pushdown optimization, the Integration Service analyzes the mapping from the source to the target or until it reaches a downstream transformation it cannot push to the target database. It generates and executes SQL statements against the source or target based on the transformation logic it can push to the database.

When you run a session with large quantities of data and full pushdown optimization, the database server must run a long transaction. Consider the following database performance issues when you generate a long transaction:

A long transaction uses more database resources.

A long transaction locks the database for longer periods of time. This reduces database concurrency and increases the likelihood of deadlock.

A long transaction increases the likelihood of an unexpected event.

To minimize database performance issues for long transactions, consider using source-side or target-side pushdown optimization.

Integration Service Behavior with Full Optimization

When you configure a session for full optimization, the Integration Service analyzes the mapping from the source to the target or until it reaches a downstream transformation it cannot push to the target database. If the Integration Service cannot push all transformation logic to the target database, it tries to push all transformation logic to the source database. If it cannot push all transformation logic to the source or target, the Integration Service pushes as much transformation logic to the source database, processes intermediate transformations that it cannot push to any database, and then pushes the remaining transformation logic to the target database. The Integration Service generates and executes an INSERT SELECT, DELETE, or UPDATE statement for each database to which it pushes transformation logic.

The Rank transformation cannot be pushed to the source or target database. If you configure the session for full pushdown optimization, the Integration Service pushes the Source Qualifier transformation and the Aggregator transformation to the source, processes the Rank transformation, and pushes the Expression transformation and target to the target database. The Integration Service does not fail the session if it can push only part of the transformation logic to the database.

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