SAP BW on HANA Interview Questions and Answers
by sonia, on Jan 11, 2018 5:25:02 PM
Q1. What is SAP BW on HANA? How It Works?Ans: When people refer to running SAP Business Information Warehouse on the SAP HANA in-memory database, or SAP BW on HANA for short, they are talking about running a particular version of SAP's BW software that uses HANA as its primary database and is specially optimized for the HANA platform.
BW supports many databases, including Oracle, MS SQL Server, DB2 and now HANA. Using BW on HANA means that no other database is required.
SAP BW is also specially optimized for HANA above and beyond its optimization for other databases. BW does have database-specific optimizations for other databases -- for example, it supports DB2's clustering concept for very large tables, whereas most other databases use a partitioning concept to handle this scenario -- but the situation with SAP HANA goes above and beyond. Activities like the activation step for DataStore Objects, or DSOs, and certain types of transformations are functionally the same on HANA as on other databases, but the actual processing has been moved into HANA rather than happening on the BW application server as it does with other databases. This cuts down on data movement, making it possible to execute these activities much faster with BW on HANA.
Other features are available only with BW on HANA. For example, the Open ODS View concept is a way to overlay such BW semantics as security and the BW analytic engine on data that is stored in tables outside of the BW system. However, Open ODS Views are enabled in BW only if it is running on top of the HANA platform, and is not available on other database platforms.
The exact features available, as well as the question of whether they are executed on HANA vs. the BW application server, changed between NetWeaver BW release 7.3 and release 7.4, so check on individual features if you are looking at BW on HANA using the 7.3 platform.
Q2. How does SAP HANA support Massively Parallel Processing?
Ans: With availability of Multi-Core CPUs, higher CPU execution speeds can be achieved.
Also, HANA Column-based storage makes it easy to execute operations in parallel using multiple processor cores.
In a column store data is already vertically partitioned. This means that operations on different columns can easily be processed in parallel. If multiple columns need to be searched or aggregated, each of these operations can be assigned to a different processor core.
In addition, operations on one column can be parallelized by partitioning the column into multiple sections that can be processed by different processor cores. With the SAP HANA database, queries can be executed rapidly and in parallel.
Q3. What is the DIM ID?
Ans: DIM ID: are used to connect fact tables and dimension tables
Q4. What is an info source?
Ans: A structure consisting of InfoObjects without persistence for connecting two transformations
Q5. What are the steps to load non-cumulative cube?
Ans: initialize opening balance in R/3 (S278)
activate extract structure MCO3BFO for data source 2LIS_03_BF
set up historical material documents in R/3
load opening balance using data source 2LIS_40_S278
load historical movements and compress without marker update.
set up V3 update
load deltas using 2LIS_03_BF.
Q6. What is a transnational info cube?
Ans: These cubes are used for both read and write; standard cubes are optimized for reading. The transactional cubes are used in SEM.
Give example data sources supporting this?
2LIS_03_BF and 2LIS_03_UM
Q7. What is a source system?
Ans: Any system that is sending data to BW like R/3, lat file, oracle database or external systems.
Q8. What is the time distribution option in update rule?
Ans: This is to distribute data per time; for example, if the source contains calendar week and the target contains calendar day, the data is spit for each calendar day. you can select either the normal calendar or the factory calendar.
Q9. What is the language SAP HANA is developed in?
Ans: The SAP HANA database is developed in C++.
Q10. What is ad hoc analysis?
Ans: In traditional data warehouses, such as SAP BW, a lot of pre-aggregation is done for quick results. That is the administrator (IT department) decides which information might be needed for analysis and prepares the result for the end users. This results in fast performance but the end user does not have flexibility.
The performance reduces dramatically if the user wants to do analysis on some data that is not already pre-aggregated. With SAP HANA and its speedy engine, no pre-aggregation is required. The user can perform any kind of operations in their reports and does not have to wait hours to get the data ready for analysis.
Q11. What are the types of attributes?
Ans: Display only and navigational; display only attributes are only for display and no analysis can be done; navigational attributes behave like regular characteristics; for example, assume that we have a customer characteristics with country as a navigational attribute; you can analyze the data using customer and country.
Q12. Mention What Is The Role Of The Transaction Manager And Session?
Ans: The transaction manager co-ordinates database transactions and keeps a record of running and closed transactions. When transaction is rolled back or committed, the transaction manager notifies the involved storage engines about the event so they can run necessary actions.
Q13. Explain How You Can Avoid Un-necessary Logging Information From Being Stored?
Ans: You can avoid un-necessary logging information from being stored by pausing the replication by stopping the schema-related jobs.
Q14. Explain How Sql Statement Is Processed?
Ans: In the HANA database, each SQL statement is implemented in the reference of the transaction. New session is allotted to a new transaction.
Q15. What are the row-based and column based approach?
Row based tables:
It is the traditional Relational Database approach
It store a table in a sequence of rows
Column based tables:
It store a table in a sequence of columns i.e. the entries of a column is stored in contiguous memory locations.
SAP HANA is particularly optimized for column-order storage.
SAP HANA supports both row-based and column-based approach.
Q16. Can you partition a cube which has data already?
Ans: No; the cube must be empty to do this; one work around is to make a copy of the cube A to cube B; export data from A to B using export data source; empty cube A; create partition on A; re-import data from B; delete cube B.
Q17. Can you disable cache?
Ans: Yes, either globally or using query debug tool RSRT.
Q18. What is global transfer nile?
Ans: This is a transfer routine (ABAP) defined at the info object level; this is common for all source systems.