1. What is an update strategy transformation?
Update strategy transformation is used to flag source rows for insert, update, delete or reject within a mapping. Based on this flagging each row will be either inserted or updated or deleted from the target. Alternatively the row can be rejected.
2. Why update strategy is an active transformation?
As update strategy transformation can reject rows, it is called as an active transformation.
3. What are the constants used in update strategy transformation for flagging the rows?
Update strategy transformation is used to flag source rows for insert, update, delete or reject within a mapping. Based on this flagging each row will be either inserted or updated or deleted from the target. Alternatively the row can be rejected.
2. Why update strategy is an active transformation?
As update strategy transformation can reject rows, it is called as an active transformation.
3. What are the constants used in update strategy transformation for flagging the rows?
· DD_INSERT is used for inserting the rows. The
numeric value is 0.
· DD_UPDATE is used for updating the rows. The
numeric value is 1.
· DD_DELETE is used for deleting the rows. The
numeric value is 2.
· DD_REJECT is used for rejecting the rows. The
numeric value is 3.
4. If you place an aggregator after the update strategy transformation, how the output of aggregator will be affected?
The update strategy transformation flags the rows for insert, update and delete of reject before you perform aggregate calculation. How you flag a particular row determines how the aggregator transformation treats any values in that row used in the calculation. For example, if you flag a row for delete and then later use the row to calculate the sum, the integration service subtracts the value appearing in this row. If the row had been flagged for insert, the integration service would add its value to the sum.
5. How to update the target table without using update strategy transformation?
In the session properties, there is an option 'Treat Source Rows As'. Using this option you can specify whether all the source rows need to be inserted, updated or deleted.
6. If you have an update strategy transformation in the mapping, what should be the value selected for 'Treat Source Rows As' option in session properties?
The value selected for the option is 'Data Driven'. The integration service follows the instructions coded in the update strategy transformation.
7. If you have an update strategy transformation in the mapping and you did not selected the value 'Data Driven' for 'Treat Source Rows As' option in session, then how the session will behave?
If you do not choose Data Driven when a mapping contains an Update Strategy or Custom transformation, the Workflow Manager displays a warning. When you run the session, the Integration Service does not follow instructions in the Update Strategy transformation in the mapping to determine how to flag rows.
8. In which files the data rejected by update strategy transformation will be written?
If the update strategy transformation is configured to Forward Rejected Rows then the integration service forwards the rejected rows to next transformation and writes them to the session reject file. If you do not select the forward reject rows option, the integration service drops rejected rows and writes them to the session log file. If you enable row error handling, the Integration Service writes the rejected rows and the dropped rows to the row error logs. It does not generate a reject file.
9. what is
data driven?
When ever a mapping contains Update Strategy Transformation the
way data needs to be treated is declared in the session property as Data Driven. This is done by
mentioning DD_UPDATE or DD_INSERT or DD_DELETE in the update strategy
transformation.
Example :
Example :
A mapping may contain two Update strategy transformations, 1
for inserting and another for Updating in two different pipelines in single mapping. Therefore, in
order session to get executed successfully, mention Data Driven property in the
session properties for that particular mapping.
The informatica server follows instructions coded into update
Strategy transformations with in the session maping determine how to flag
records for insert,update,,delete or reject If u do not choose data driven
option setting,the informatica server ignores all update strategy
transformations in the mapping
10.What is Update Strategy ?
Update strategy is used to decide on how you will handle updates in your
project.
When you design your data warehouse, you need to decide what type of information to store
in targets. As part of your target table design, you need to determine whether to maintain all
the historic data or just the most recent changes.
For example, you might have a target table, T_CUSTOMERS, that contains customer data.
When a customer address changes, you may want to save the original address in the table
instead of updating that portion of the customer row. In this case, you would create a new row
containing the updated address, and preserve the original row with the old customer address.
This illustrates how you might store historical information in a target table. However, if you
want the T_CUSTOMERS table to be a snapshot of current customer data, you would
update the existing customer row and lose the original address.
The model you choose determines how you handle changes to existing rows.
In PowerCenter, you set your update strategy at two different levels:
1) Within a session. When you configure a session, you can instruct the PowerCenter Server
to either treat all rows in the same way (for example, treat all rows as inserts), or use
instructions coded into the session mapping to flag rows for different database operations.
2) Within a mapping. Within a mapping, you use the Update Strategy transformation to flag
rows for insert, delete, update, or reject.
Note: You can also use the Custom transformation to flag rows for insert, delete, update, or reject.
When you design your data warehouse, you need to decide what type of information to store
in targets. As part of your target table design, you need to determine whether to maintain all
the historic data or just the most recent changes.
For example, you might have a target table, T_CUSTOMERS, that contains customer data.
When a customer address changes, you may want to save the original address in the table
instead of updating that portion of the customer row. In this case, you would create a new row
containing the updated address, and preserve the original row with the old customer address.
This illustrates how you might store historical information in a target table. However, if you
want the T_CUSTOMERS table to be a snapshot of current customer data, you would
update the existing customer row and lose the original address.
The model you choose determines how you handle changes to existing rows.
In PowerCenter, you set your update strategy at two different levels:
1) Within a session. When you configure a session, you can instruct the PowerCenter Server
to either treat all rows in the same way (for example, treat all rows as inserts), or use
instructions coded into the session mapping to flag rows for different database operations.
2) Within a mapping. Within a mapping, you use the Update Strategy transformation to flag
rows for insert, delete, update, or reject.
Note: You can also use the Custom transformation to flag rows for insert, delete, update, or reject.
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