Below are some important Data Warehouse interview questions which are asked in most MNC company interviews for beginners or professionals.
1. How can we run the graph? What is the procedure for that? How can we schedule the graph in UNIX?
If you want to run the graph through GDE then after save the graph just press F5 button of your keyboard, it will run automatically. If you want to run through the shell script then you have to fire the command at your UNIX box.
2. What is a real-time data warehouse? How is it different from near to real-time data warehouse?
As the term suggests, a real-time data warehouse is a system, which reflects all changes to its sources in real time. As simple as it sounds, this is still an area of active research in the field. In traditional DWH, the operational system(s) are kept separate from the DWH for a good reason. The Operational systems are designed to accept inputs or changes to data regularly, hence have a good chance of being regularly queried. On the other hand, a DWH is supposed to do just the opposite - it is
used to query data for reports only. No changes to data, through user actions is expected (or designed). The only inputs could come from the ETL feed at stipulated times. The ETL would source its data from the Operational systems just explained above.
To create a real-time DWH we would have to merge both systems (several ways are being explored), a concept that is against the reason of creating a DWH. Bigger challenges occur in terms of updating aggregated data in facts at real time, still maintaining the surrogate keys. Besides, we would need lightening fast hardware to try this.Near Real time DWH is a trade-off between the conventional design and the dream of all clients today. The frequency of ETL updates in higher in this case for
e.g. once in 2 hours. We can also analyze and use selective refreshes at shorter time intervals, while complete refreshes may still be kept further apart. Selective refreshes would look at only those tables that get updated regularly.
3. What is difference between drill & scope of analysis?
Drilling can be done in drill down, up, through, and across; scope is the overall view of the drill exercise.
4. I have two Universes created by two difference database can we join them in Designer & Report level? How
We can link one universe to other universe in Universe parameters.
5. For faster process, what we will do with the Universe?
For a faster process create aggregate tables and write better sql so that the process would fast.
6. What is type 2 version dimension?
Version dimension is the SCD type II in real time it using because of it will maintain the current data and full historical data.
7. What is unit testing?
The Developer created the mapping that can be tested independently by the developer individually.
8. What is Informatica Architecture?
Informatica Architecture contains Repository, Repository server, Repository server administration console, sources, repository server and Data warehousing and it have the Designer, Work for manager, work for monitor combination of all these are called Informatica Architecture.
9. What is data warehouse architecture?
Data warehousing is the repository of integrated information data will be extracted from the heterogeneous sources. Data warehousing architecture contains the different; sources like oracle, flat files and ERP then after it have the staging area and Data warehousing, after that it has the different Data marts then it have the reports and it also have the ODS - Operation Data Store. This complete architecture is called the Data warehousing Architecture.
10. What is data analysis? Where it will be used?
Data analysis: consider that you are running a business and you store the data of that; in some form say in register or in a comp and at the year end you want know the profit or loss then it called data analysis .Data analysis use: then you want to know which product was sold the highest and if the business is running in a loss then finding, where we went wrong we do analysis.
1. How can we run the graph? What is the procedure for that? How can we schedule the graph in UNIX?
If you want to run the graph through GDE then after save the graph just press F5 button of your keyboard, it will run automatically. If you want to run through the shell script then you have to fire the command at your UNIX box.
2. What is a real-time data warehouse? How is it different from near to real-time data warehouse?
As the term suggests, a real-time data warehouse is a system, which reflects all changes to its sources in real time. As simple as it sounds, this is still an area of active research in the field. In traditional DWH, the operational system(s) are kept separate from the DWH for a good reason. The Operational systems are designed to accept inputs or changes to data regularly, hence have a good chance of being regularly queried. On the other hand, a DWH is supposed to do just the opposite - it is
used to query data for reports only. No changes to data, through user actions is expected (or designed). The only inputs could come from the ETL feed at stipulated times. The ETL would source its data from the Operational systems just explained above.
To create a real-time DWH we would have to merge both systems (several ways are being explored), a concept that is against the reason of creating a DWH. Bigger challenges occur in terms of updating aggregated data in facts at real time, still maintaining the surrogate keys. Besides, we would need lightening fast hardware to try this.Near Real time DWH is a trade-off between the conventional design and the dream of all clients today. The frequency of ETL updates in higher in this case for
e.g. once in 2 hours. We can also analyze and use selective refreshes at shorter time intervals, while complete refreshes may still be kept further apart. Selective refreshes would look at only those tables that get updated regularly.
3. What is difference between drill & scope of analysis?
Drilling can be done in drill down, up, through, and across; scope is the overall view of the drill exercise.
4. I have two Universes created by two difference database can we join them in Designer & Report level? How
We can link one universe to other universe in Universe parameters.
5. For faster process, what we will do with the Universe?
For a faster process create aggregate tables and write better sql so that the process would fast.
6. What is type 2 version dimension?
Version dimension is the SCD type II in real time it using because of it will maintain the current data and full historical data.
7. What is unit testing?
The Developer created the mapping that can be tested independently by the developer individually.
8. What is Informatica Architecture?
Informatica Architecture contains Repository, Repository server, Repository server administration console, sources, repository server and Data warehousing and it have the Designer, Work for manager, work for monitor combination of all these are called Informatica Architecture.
9. What is data warehouse architecture?
Data warehousing is the repository of integrated information data will be extracted from the heterogeneous sources. Data warehousing architecture contains the different; sources like oracle, flat files and ERP then after it have the staging area and Data warehousing, after that it has the different Data marts then it have the reports and it also have the ODS - Operation Data Store. This complete architecture is called the Data warehousing Architecture.
10. What is data analysis? Where it will be used?
Data analysis: consider that you are running a business and you store the data of that; in some form say in register or in a comp and at the year end you want know the profit or loss then it called data analysis .Data analysis use: then you want to know which product was sold the highest and if the business is running in a loss then finding, where we went wrong we do analysis.
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