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Thursday, September 26, 2013

Interview Questions : DataStage - Part 2

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What is the importance of Surrogate Key in Data warehousing?
Ans : Surrogate Key is a Primary Key for a Dimension table. Most importance of using it is independent of underlying database. i.e Surrogate Key is not affected by the changes going on with a database

What does a Config File in parallel extender consist of?
Ans: Config file consists of the following.
a) Number of Processes or Nodes.
b) Actual Disk Storage Location.

How many places you can call Routines?
Ans:  Four Places you can call
(i) Transform of routine
       (A) Date Transformation
       (B) Upstring Transformation
(ii) Transform of the Before & After Subroutines
(iii) XML transformation
(iv)Web base

How did you handle an 'Aborted' sequencer?
Ans: In almost all cases we have to delete the data inserted by this from DB manually and fix the job and then run the job again.

Is it possible to calculate a hash total for an EBCDIC file and have the hash total stored as EBCDIC using Datastage ?
Ans: Currently, the total is converted to ASCII, even tho the individual records are stored as EBCDIC.

Compare and Contrast ODBC and Plug-In stages?
Ans: ODBC :
a) Poor Performance.
b) Can be used for Variety of Databases.
c) Can handle Stored Procedures.
Plug-In: a) Good Performance. b) Database specific.(Only one database)

What is Functionality of Link Partitioner and Link Collector?
Ans: Link Partitioner is partitioned the data the node defined in Configuration File.
Link Collector is collect the partitioned data.

Containers : Usage and Types?
Containers is a collection of stages used for the purpose of Reusability. There are 2 types of Containers. a) Local Container: Job Specific b) Shared Container: Used in any job within a project.

Explain Dimension Modeling types along with their significance
Ans: Data Modelling is Broadly classified into 2 types. a) E-R Diagrams (Entity - Relatioships). b) Dimensional Modelling.

Did you Parameterize the job or hard-coded the values in the jobs?
Ans: Always parameterized the job. Either the values are coming from Job Properties or from a ‘Parameter Manager’ – a third part tool. There is no way you will hard–code some parameters in your jobs.

How did you connect with DB2 in your last project?
Ans: Most of the times the data was sent to us in the form of flat files. The data is dumped and sent to us. In some cases were we need to connect to DB2 for look-ups as an instance then we used ODBC drive.

What are the often used Stages or stages you worked with in your last project?
Ans: A) Transformer, ORAOCI8/9, ODBC, Link-Partitioner, Link-Collector, Hash, ODBC, Aggregator, Sort.