4/11/16

Informatica Interview Questions and Answers-3

Question.1 What is Data warehouse?

Answer: According to Bill Inmon, known as father of Data warehousing. “A Data warehouse is a subject oriented, integrated ,time variant, non volatile collection of data in support of management’s decision making process”.
Question.2 What are the types of data warehouses?
Answer: There are three types of data warehouses
                 Enterprise Data Warehouse
                 ODS (operational data store)
                 Data Mart 
Question.3 What is Data mart?
Answer: A data mart is a subset of data warehouse that is designed for a particular line of business, such as sales, marketing, or finance. In a dependent data mart, data can be derived from an enterprise wide data warehouse. In an independent data mart can be collected directly from sources.
Question.4 What is star schema?
Answer: A star schema is the simplest form of data warehouse schema that consists of one or more dimensional and fact tables.
Question.5 What is snow flake schema?
Answer: A Snowflake schema is nothing but one Fact table which is connected to a number of dimension tables, The snowflake and star schema are methods of storing data which are multidimensional in nature.
Question.6 What are ETL Tools?
Answer: ETL Tools are stands for Extraction, Transformation, and Loading the data into the data warehouse for decision making. ETL refers to the methods involved in accessing and manipulating source data and loading it into target database.
Question.7 What are Dimensional table?
Answer: Dimension tables contain attributes that describe fact records in the fact table.
Question.8 What is data Modelling?
Answer: Data Modeling is representing the real world set of data structures or entities and their relationship in their of data models, required for a database.Data Modelling consists of various types like
              Conceptual data modeling
              Logical data modeling
              Physical data modeling
              Enterprise data modeling
              Relation data modeling
              Dimensional data modeling.
Question.9 What is Surrogate key?
Answer: Surrogate key is a substitution for the natural primary key. It is just a unique identifier or number of each row that can be used for the primary key to the table.
Question.10 What is Data Mining?
Answer: A Data Mining is the process of analyzing data from different perspectives and summarizing it into useful information.
Question.11 What is Operational Data Store?
Answer: A ODS is an operational data store which comes as a second layer in a datawarehouse architecture. It has got the characteristics of both OLTP and DSS systems.
Question.12 What is the Difference between OLTP and OLAP?
Answer: OLTP is nothing but OnLine Transaction Processing which contains a normalisedtables
But OLAP(Online Analtical Programming) contains the history of OLTP data which is non-volatile acts as a Decisions Support System.
Question.13 How many types of dimensions are available in Informatica?
Answer: There are three types of dimensions available are :
                     Junk dimension
                     Degenerative Dimension
                     Conformed Dimension
Question.14 What are the designer tools for creating tranformations?
Answer:     Mapping designer
                     Transformation developer
                     Mapplet designer
Question.15 What is the maplet?
Answer: Maplet is a set of transformations that you build in the maplet designer and you can use in multiple mapings.
Question. 16 What is Session and Batches?
Answer: Session: A session is a set of commands that describes the server to move data to the target.Batch: A Batch is set of tasks that may include one or more numbar of tasks (sessions, ewent wait, email, command, etc).
Question.17 What are slowly changing dimensions?
Answer: Dimensions that change overtime are called Slowly Changing Dimensions(SCD).
Slowly Changing Dimension-Type1 : Which has only current records.
Slowly Changing Dimension-Type2 : Which has current records + historical records.
Slowly Changing Dimension-Type3 : Which has current records + one previous records.  
Question.18 What are 2 modes of data movement in Informatica Server?
Answer: There are two modes of data movement are:
Normal Mode in which for every record a separate DML stmt will be prepared and executed.
Bulk Mode in which for multiple records DML stmt will be preapred and executed thus improves performance.
Question.19 What is the difference between Active and Passive transformation?
Answer: Active Transformation:An active transformation can change the number of rows that pass through it from source to target i.e it eliminates rows that do not meet the condition in transformation.Passive Transformation:A passive transformation does not change the number of rows that pass through it i.e it passes all rows through the transformation.