informatica interview Question Part-1

Informatica Architecture

The Power Center domain

            It is a primary unit of the Administration.

            Can have single and multiple domains.

            It is a collection of nodes and services.

Nodes

   A node is the logical representation of a machine in a domain

One node in the domain acts as a gateway node to receive service requests from clients and route them to the appropriate service and node

Integration Service:

Integration Service does all the real job. It extracts data from sources, processes it as   per the business logic and loads data to targets.

Repository Service:

Repository Service is used to fetch the data from the repository and sends it back to the     requesting components (mostly client tools and integration service)

Power Center Repository:

Repository is nothing but a relational database which stores all the metadata created in  Power Center.

Power Center Client Tools:

 The Power Center Client consists of multiple tools.

Power Center Administration Console:

This is simply a web-based administration tool you can use to administer the Power Center installation.

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

• Custom

• Expression

• External Procedure

• Filter

• Input

• Joiner

• Lookup

• Normalizer

• 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 rowby-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 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. What are the types of loading in Informatica?

There are two types of loading, 1. Normal loading and 2. Bulk loading.

In normal loading, it loads record by record and writes log for that. It takes comparatively a longer time to load data to the target.

In bulk loading, it loads number of records at a time to target database. It takes less time to load data to target.

Q. What is aggregate cache in aggregator transformation? 

The aggregator stores data in the aggregate cache until it completes aggregate calculations. When you run a session that uses an aggregator transformation, the informatica server creates index and data caches in memory to process the transformation. If the informatica server requires more space, it stores overflow values in cache files. 

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 its 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.