Informatica Interview Questions 1

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Informatica Repository Manager

Q. What type of repositories can be created using Informatica Repository Manager?

A. Informatica PowerCenter includes following type of repositories:

  • Standalone Repository: A repository that functions individually and this is unrelated to any other repositories.
  • Global Repository: This is a centralized repository in a domain. This repository can contain shared objects across the repositories in a domain. The objects are shared through global shortcuts.
  • Local Repository: Local repository is within a domain and it’s not a global repository. Local repository can connect to a global repository using global shortcuts and can use objects in it’s shared folders.
  • Versioned Repository: This can either be local or global repository but it allows version control for the repository. A versioned repository can store multiple copies, or versions of an object. This feature allows efficiently developing, testing and deploying metadata in the production environment.

Q. What is a code page?

A. A code page contains encoding to specify characters in a set of one or more languages. The code page is selected based on source of the data. For example if source contains Japanese text then the code page should be selected to support Japanese text.

When a code page is chosen, the program or application for which the code page is set, refers to a specific set of data that describes the characters the application recognizes. This influences the way that application stores, receives, and sends character data.

Q. Which all databases PowerCenter Server on Windows can connect to?

A. PowerCenter Server on Windows can connect to following databases:

  • IBM DB2
  • Informix
  • Microsoft Access
  • Microsoft Excel
  • Microsoft SQL Server
  • Oracle
  • Sybase
  • Teradata

Q. Which all databases PowerCenter Server on UNIX can connect to?

A. PowerCenter Server on UNIX can connect to following databases:

  • IBM DB2
  • Informix
  • Oracle
  • Sybase
  • Teradata

Informatica Mapping Designer

Q. How to execute PL/SQL script from Informatica mapping?

A. Stored Procedure (SP) transformation can be used to execute PL/SQL Scripts. In SP Transformation PL/SQL procedure name can be specified. Whenever the session is executed, the session will call the pl/sql procedure.

Q. How can you define a transformation? What are different types of transformations available in Informatica?

A. A transformation is a repository object that generates, modifies, or passes data. The Designer provides a set of transformations that perform specific functions. For example, an Aggregator transformation performs calculations on groups of data. Below are the various transformations available in Informatica:

  • Aggregator
  • Application Source Qualifier
  • Custom
  • Expression
  • External Procedure
  • Filter
  • Input
  • Joiner
  • Lookup
  • Normalizer
  • Output
  • Rank
  • Router
  • Sequence Generator
  • Sorter
  • Source Qualifier
  • Stored Procedure
  • Transaction Control
  • Union
  • Update Strategy
  • XML Generator
  • XML Parser
  • XML Source Qualifier

Q. What is a source qualifier? What is meant by Query Override?

A. Source Qualifier represents the rows that the PowerCenter Server reads from a relational or flat file source when it runs a session. When a relational or a flat file source definition is added to a mapping, it is connected to a Source Qualifier transformation.

PowerCenter Server generates a query for each Source Qualifier Transformation whenever it runs the session. The default query is SELET statement containing all the source columns. Source Qualifier has capability to override this default query by changing the default settings of the transformation properties. The list of selected ports or the order they appear in the default query should not be changed in overridden query.

Q. What is aggregator transformation?

A. The Aggregator transformation allows performing aggregate calculations, such as averages and sums. Unlike Expression Transformation, the Aggregator transformation can only be used to perform calculations on groups. The Expression transformation permits calculations on a row-by-row basis only.

Aggregator Transformation contains group by ports that indicate how to group the data. While grouping the data, the aggregator transformation outputs the last row of each group unless otherwise specified in the transformation properties.

Various group by functions available in Informatica are : AVG, COUNT, FIRST, LAST, MAX, MEDIAN, MIN, PERCENTILE, STDDEV, SUM, VARIANCE.

Q. What is Incremental Aggregation?

A. Whenever a session is created for a mapping Aggregate Transformation, the session option for Incremental Aggregation can be enabled. When PowerCenter performs incremental aggregation, it passes new source data through the mapping and uses historical cache data to perform new aggregation calculations incrementally.

Q. How Union Transformation is used?

A. The union transformation is a multiple input group transformation that can be used to merge data from various sources (or pipelines). This transformation works just like UNION ALL statement in SQL that is used to combine result set of two SELECT statements.

Q. Can two flat files be joined with Joiner Transformation?

A. Yes, joiner transformation can be used to join data from two flat file sources.

Q. What is a look up transformation?

A. This transformation is used to lookup data in a flat file or a relational table, view or synonym. It compares lookup transformation ports (input ports) to the source column values based on the lookup condition. Later returned values can be passed to other transformations.

Q. Can a lookup be done on Flat Files?

A. Yes.

Q. What is the difference between a connected look up and unconnected look up?

A. Connected lookup takes input values directly from other transformations in the pipeline.

Unconnected lookup doesn’t take inputs directly from any other transformation, but it can be used in any transformation (like expression) and can be invoked as a function using: LKP expression. So, an unconnected lookup can be called multiple times in a mapping.

Q. What is a mapplet?

A. A mapplet is a reusable object that is created using mapplet designer. The mapplet contains set of transformations and it allows us to reuse that transformation logic in multiple mappings.

Q. What does reusable transformation mean?

A. Reusable transformations can be used multiple times in a mapping. The reusable transformation is stored as a metadata separate from any other mapping that uses the transformation. Whenever any changes to a reusable transformation are made, all the mappings where the transformation is used will be invalidated.

Q. What is update strategy and what are the options for update strategy?

A. Informatica processes the source data row-by-row. By default every row is marked to be inserted in the target table. If the row has to be updated/inserted based on some logic Update Strategy transformation is used. The condition can be specified in Update Strategy to mark the processed row for update or insert.

Following options are available for update strategy:

  • DD_INSERT : If this is used the Update Strategy flags the row for insertion. Equivalent numeric value of DD_INSERT is 0.
  • DD_UPDATE : If this is used the Update Strategy flags the row for update. Equivalent numeric value of DD_UPDATE is 1.
  • DD_DELETE : If this is used the Update Strategy flags the row for deletion. Equivalent numeric value of DD_DELETE is 2.
  • DD_REJECT : If this is used the Update Strategy flags the row for rejection. Equivalent numeric value of DD_REJECT is 3.

Q. I wanted to load only particular no of records suppose i have 100 records out of which i wanted to load first 10 records to target.

A. Select only 10 records in your source qualifier query.
You can use rownum function in oracle to select 10 records.

Q. If one wants to see the time dependent master data, what table is to be referred?

a. Master file

Q. The difference between Oracle Sequence Generator and Informatica Sequence Generator? Which is faster in performance? Which is best to use?

a. Informatica Sequence Gen uses its server cache and generates the sequence numbers and uses it along with the load which happens at the same time remember it will use the Informatica Cache which is comparatively not that big with transformations like Lookup and others…. Advantage is very easy to create and use it when we are inserting into multiple targets! Infa seq is part and parcel of mapping(s).
But in case of Oracle Sequence we need to maintain it separately along with tables and other objects and the main question is how will you access it every time in every mapping.

Q. What are the Tracking levels in Informatica transformations? Which one is efficient and which one faster and which one is best in Informatica Power Centre 8.1/8.5?

a. 1.Normal: Integration Service logs initialization and status information, errors encountered and skipped rows due to transformation row errors. Summarizes session results, but not at the level of individual rows.

2. Terse: Integration Service logs initialization information and error messages and notification of rejected data.

3. Verbose Initialization: In addition to normal tracing, Integration Service logs additional initialization details, names of index and data files used, and detailed transformation statistics.

4. Verbose Data: In addition to verbose initialization tracing, Integration Service logs each row that passes into the mapping. Also notes where the Integration Service truncates string data to fit the precision of a column and provides detailed transformation statistics.
Allows the Integration Service to write errors to both the session log and error log when you enable row error logging.
When you configure the tracing level to verbose data, the Integration Service writes row data for all rows in a block when it processes a transformation.
By default, the tracing level for every transformation is Normal.

Q. What are all the new features of informatica 8.1?

A.. Power Center 8 release has “Append to Target file” feature.

  1. Java transformation is introduced.
  2. User defined functions
  3. Midstream SQL transformation has been added in 8.1.1 not in 8.1.
  4. Informatica has added a new web based administrative console.
  5. Management is centralized that means services can be started and stopped on nodes via a central web interface.

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1 Comment

  • ankit kansal says on September 5, 2014 at 3:16 am | Permalink

    Thanks for sharing the information , I was looking for the same topic over the internet. Thanks once again.

    Ankit Kansak
    deepinopensource.com/

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