Informatica Interview Questions

1.What are the differences between Connected and Unconnected Lookup?

The differences are illustrated in the below table:

Connected Lookup	Unconnected Lookup
Connected lookup participates in dataflow and receives input directly from the pipeline	Unconnected lookup receives input values from the result of a LKP: expression in another transformation
Connected lookup can use both dynamic and static cache	Unconnected Lookup cache can NOT be dynamic
Connected lookup can return more than one column value ( output port )	Unconnected Lookup can return only one column value i.e. output port
Connected lookup caches all lookup columns	Unconnected lookup caches only the lookup output ports in the lookup conditions and the return port
Supports user-defined default values (i.e. value to return when lookup conditions are not satisfied)	Does not support user defined default values

2.What is meant by active and passive transformation?

An active transformation is the one that performs any of the following actions:

1. Change the number of rows between transformation input and output. Example: Filter transformation
2. Change the transaction boundary by defining commit or rollback points., example transaction control transformation
3. Change the row type, example Update strategy is active because it flags the rows for insert, delete, update or reject

On the other hand a passive transformation is the one which does not change the number of rows that pass through it. Example: Expression transformation.

3.Why is Sorter an Active Transformation?
This is because we can select the "distinct" option in the sorter property.

When the Sorter transformation is configured to treat output rows as distinct, it assigns all ports as part of the sort key. The Integration Service discards duplicate rows compared during the sort operation. The number of Input Rows will vary as compared with the Output rows and hence it is an Active transformation

4.What are the new features of Informatica 9.x in developer level?

From a developer's perspective, some of the new features in Informatica 9.x are as follows:

• Now Lookup can be configured as an active transformation – it can return multiple rows on successful match
• Now you can write SQL override on un-cached lookup also. Previously you could do it only on cached lookup
• You can control the size of your session log. In a real-time environment you can control the session log file size or time
• Database deadlock resilience feature – this will ensure that your session does not immediately fail if it encounters any database deadlock, it will now retry the operation again. You can configure number of retry attempts.

Revisiting Rank Transformation

Q5. What is a Rank Transform?

Ans. Rank is an Active Connected Informatica transformation used to select a set of top or bottom values of data.

6. How does a Rank Transform differ from Aggregator Transform functions MAX and MIN?

Ans. Like the Aggregator transformation, the Rank transformation lets us group information. The Rank Transform allows us to select a group of top or bottom values, not just one value as in case of Aggregator MAX, MIN functions.

7. What is a RANK port and RANKINDEX?

Ans. Rank port is an input/output port use to specify the column for which we want to rank the source values. By default Informatica creates an output port RANKINDEX for each Rank transformation. It stores the ranking position for each row in a group.

8. How can you get ranks based on different groups?

Ans. Rank transformation lets us group information. We can configure one of its input/output ports as a group by port. For each unique value in the group port, the transformation creates a group of rows falling within the rank definition (top or bottom, and a particular number in each rank).

9. What happens if two rank values match?

Ans. If two rank values match, they receive the same value in the rank index and the transformation skips the next value.

10. What are the restrictions of Rank Transformation?

Ans.

• We can connect ports from only one transformation to the Rank transformation.
• We can select the top or bottom rank.
• We need to select the Number of records in each rank.
• We can designate only one Rank port in a Rank transformation.

11. How does a Rank Cache works?

Ans. During a session, the Integration Service compares an input row with rows in the data cache. If the input row out-ranks a cached row, the Integration Service replaces the cached row with the input row. If we configure the Rank transformation to rank based on different groups, the Integration Service ranks incrementally for each group it finds. The Integration Service creates an index cache to stores the group information and data cache for the row data.

12. How does Rank transformation handle string values?

Ans. Rank transformation can return the strings at the top or the bottom of a session sort order. When the Integration Service runs in Unicode mode, it sorts character data in the session using the selected sort order associated with the Code Page of IS which may be French, German, etc. When the Integration Service runs in ASCII mode, it ignores this setting and uses a binary sort order to sort character data.

Revisiting Sorter Transformation

13. What is a Sorter Transformation?

Ans. Sorter Transformation is an Active, Connected Informatica transformation used to sort data in ascending or descending order according to specified sort keys. The Sorter transformation contains only input/output ports.

14. Why is Sorter an Active Transformation?

Ans. When the Sorter transformation is configured to treat output rows as distinct, it assigns all ports as part of the sort key. The Integration Service discards duplicate rows compared during the sort operation. The number of Input Rows will vary as compared with the Output rows and hence it is an Active transformation.

15. How does Sorter handle Case Sensitive sorting?

Ans. The Case Sensitive property determines whether the Integration Service considers case when sorting data. When we enable the Case Sensitive property, the Integration Service sorts uppercase characters higher than lowercase characters.

16. How does Sorter handle NULL values?

Ans. We can configure the way the Sorter transformation treats null values. Enable the property Null Treated Low if we want to treat null values as lower than any other value when it performs the sort operation. Disable this option if we want the Integration Service to treat null values as higher than any other value.

17. How does a Sorter Cache works?

Ans. The Integration Service passes all incoming data into the Sorter Cache before Sorter transformation performs the sort operation.

The Integration Service uses the Sorter Cache Size property to determine the maximum amount of memory it can allocate to perform the sort operation. If it cannot allocate enough memory, the Integration Service fails the session. For best performance, configure Sorter cache size with a value less than or equal to the amount of available physical RAM on the Integration Service machine.

If the amount of incoming data is greater than the amount of Sorter cache size, the Integration Service temporarily stores data in the Sorter transformation work directory. The Integration Service requires disk space of at least twice the amount of incoming data when storing data in the work directory.