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what is transformation?

Transformation is repository object that generates modifies or passes data.


what are the type of transformations?

2 types:

1) active

2) passive.

Explain active and passive transformation?

Active transformation can change the number of rows that pass through it.No of output rows less than or equal to no of input rows.

Passive transformation does not change the number of rows.Always no of output rows equal to no of input rows.

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Difference filter and router transformation.

Filter transformation to filter the data only one condition and drop the rows don’t meet the condition.

Drop rows does not store any ware like session log file..

Router transformation to filter the data based on multiple conditions and give yiou the option to route rows that don’t match to a default group.

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Explain incremental aggregation?

When using incremental aggregation you apply captured changes in the source to aggregate calculations in a session.If the source changes only incrementally and you can capture changes you can configure the session to process only those changes. This allows the power center server to update your target incrementally rather than forcing it to process the entire source and recalculate the same data each time you run the session.

You can capture new source data.use incremental aggregation when you can capture new source data much time you run the session.Use a stored procedure on filter transformation only new data.

Incremental changes do not significantly change the target.Use incremental aggregation when the changes do not significantly change the target.If processing the incrementally changed source alters more than half the existing target, the session may not benefit from using incremental aggregation. In this case drop the table and recreate the target with complete source data.

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What is a constraint based loading?


When you select this option the power center server orders the target load on a row-by-row basis only.

Edit tasks->properties->select treat source rows as insert.

Edit tasks->config object tab->select constraint based

If session is configured constraint absed loading when target table receive rows from different sources.The power center server revert the normal loading for those tables but loads all other targets in the session using constraint based loading when possible loading the primary key table first then the foreign key table.

Use the constraint based loading only when the session option treat rows as set to insert.

Constraint based load ordering functionality which allows developers to read the source once and populate parent and child tables in a single process.

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Explain bulk loading?


You can use bulk loading to improve performance of a session that inserts a large amount of data to a db2,sysbase,oracle or MS SQL server database.

When bulk loading the power center server by passes the database log,which speeds performance.

With out writing to the database log, however the target database can’t perform rollback. As a result you may not be perform recovery.

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