DataStage Interview Questions with Answers

3/12/2010 No Comment

DataStage Interview Questions with Answers.

Can you tell me whether the selection of 'Clear the table and Insert rows' in the ODBC stage send a Truncate statement to the DB or does it do some kind of Delete logic.
Answer : There is no TRUNCATE on ODBC stages. It is Clear table blah blah and that is a delete from statement. On an OCI stage such as Oracle, you do have both Clear and Truncate options. They are radically different in permissions.

Describe one situation from your project, where you had faced problem in Datastage and how did you solve it?

Answer : The jobs in which data is read directly from OCI stages are running extremely slow, giving rise to performance problems. We had to stage the data before sending to the transformer to make the jobs run faster. The job aborts in the middle of loading some 500,000 rows. Have an option either cleaning/deleting the loaded data and then run the fixed job or run the job again from the row the job has aborted, to make sure the load is proper we opted the former.

Explain why it is advisable to load the dimensional tables first and then fact tables?

Answer : As we load the dimensional tables the keys (primary) are generated and these keys (primary) are Foreign keys in Fact tables.

Explain how can you determine the sequence of jobs to load into data warehouse?

Answer : Firstly, we have to execute the jobs that load the data into Dimension tables, and then Fact tables, then load the Aggregator tables if there is any.

Name the command line functions that import and export the Datastage jobs?

Answer : The command line functions are cited below.
A. dsimport.exe- imports the DataStage components.
B. dsexport.exe- exports the DataStage components.

Name the utility you use to schedule jobs on a UNIX server other than Ascential Director?

Answer : By using the crontab utility along with dsexecute() function along with proper parameters passed.

Explain how can you call an external Java function which are not supported by DataStage?

Answer : In datastage starting from DS 6.0 we have the ability to call external Java functions using a Java package from Ascential. In this case, we can even use the command line to invoke the Java function and write the return values from the Java program (if any) and use that files as a source in DataStage job.

What will you do when you receive a file and use that file as an input or reference and then run job.

Answer : A. Under Windows: Use the 'WaitForFileActivity' under the Sequencers and then run the job. May be you can schedule the sequencer around the time the file is expected to arrive.
B. Under UNIX: Poll for the file. Once the file has start the job or sequencer depending on the file.

Explain how did you connect with DB2 database?

Answer : Most of the times the data was 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 drivers to connect to DB2 (or) DB2-UDB depending the situation and availability. Certainly DB2-UDB is better in terms of performance as you know the native drivers are always better than ODBC drivers. 'iSeries Access ODBC Driver' - ODBC drivers to connect to AS400/DB2.

What do you mean by Sequencers in Datastage?
Answer : Sequencers are job control programs that execute other jobs with preset Job parameters.

Differentiate between Primary Key and Partition Key?

Answer : Primary Key is a combination of unique and not null key. It can be a collection of key values called as composite primary key. Partition Key is nothing but just a part of Primary Key

Can you tell me how did you handle an 'Aborted' sequencer in Datastage?

Answer : In almost all the cases encountered,  we have to delete the data inserted by this from DB manually and fix the job and then run the job again to handle the 'Aborted'.
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