SAP BI/BW Interview Questions and Answers

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1. What is BW Statistics and how is it used?

The set of info cubes delivered by SAP as a part of SAP BIW which are useful in measuring the performance of how quickly a query is calculated, or how quickly data in loaded into BW and so on. BW statistics are the name suggest are useful in showing data about the costs associated with BW queries, aggregative data, OLAP, SAP business warehouse management.

2. In Data Ware housing what are the nine decision points used in BW ?

The nine Decision Points of Data Warehousing are:

Identify Dimension Tables. Identify Attributes of entities. Define granularity of the fact table. Pre Calculated Key figures. Slowly changing dimensions. Define attributes of entities. How long data will be kept. Aggregates. How often data is extracted.

3. How the dimensions are optimized? It system can be used as many as possible for

performance, for instance it may be assumed that 100 products and 200 customers; if one dimension for both, the size of the dimension will be 20000; if it was made individual dimensions then the total number of rows will be 300. Even if they are taken more than one characteristic per dimension, the math considering worst case and decide which characteristics may be combined in a dimension.

4. As per the update rule what are the conversion routines for units and currencies?

As per the update rule, the Time dimensions are automatically converted for example if the cube contains calendar month and the transfer structure contains date, the to calendar month is converted automatically.

5. What are the advantages of SID table?

The SIC table Surrogate ID table is the interface between master data and the dimension table, and the advantages are:

Uses Numeric as indexes for faster access. Master Data independent of info cubes. Language support. Slowly changing dimension support.

6. How can an info object as info provider and why?

When the report on characteristics or master data, it can make them as info provided for example make CUSTOMER as info provided and do Bex reporting on CUSTOMER, right click on the info area and select “Insert Characteristic as data target”.

7.What other tables are created for master data?

The tables that are created for master data are: M view – Combines P and Q tables. P table – Time independent master data attributes. Q table – Time Dependent master data attributes. X table – Interface between master data SID and

time independent navigational attributes SID where P is linked to the X table.

Y table – Interface between master data SID and time dependent navigational attributes SID where Q is linked to the Y table

8. What steps are involved to upload non cumulative cubes?

The steps that are involved to upload non cumulative cubes are:

Initialize opening balance in R/3 (S278). Activate extract structure MC03BF0 for data

source 2LIS_03_BF. Setup historical material documents in R/3. Load opening balance using data source

2LIS_40_s278. Load historical movements and compress without

marker update. Setup V3 update. Load deltas using 2LIS_03_BF.

9. What are the load process and processing?

The load process and processing are the Info package, Read PSA and update data target, save hierarchy, update ODS data object, data export open hub, delete overlapping requests.

10. What is the data target administration task?

The data target administration target is to delete index, generate index, construct database statistic, initial fill of new aggregates, roll up of filled aggregates, compression of the info cubes, activate ODS, complete deletion of data target.

11. Give the Step to Step approach to archiving cubes?

The Step to Step approach to Archiving Cubes is: Double click on the cube or right click and select change. Extras > Select archival. Choose fields for selection like 0CALDAY, 0CUSTOMER,

etc. Define the file structure maximum file size and maximum

number of data objects. Select the folder logical file name. Select the delete options not scheduled, start

automatically or after event. Activate the cube.Cube is ready for archival.

12. When there is a locking problems what is the parallel process?

The parallel process for locking problems: Hierarchy attributes change run. Loading master data from same info objects, for

example avoiding master data from different sources system at the same time.

Rolling up for the same info cube. Selecting deletions of info cube/ODS and parallel

loading. Activation or deletion of ODS object when

loading parallel.

13. What is the procedure to convert an info package group into a process chain?

The procedure to convert an info package group into a process chain is by double clicking on the info package group, click on the Process Chain Maintenance button and type in the name and description, the individual info packages are inserted automatically.

14. How can a cube partitioned for which the data already exists?

The cube cannot be partitioned if the data already exists 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, and delete cube B.

15. How can we perform Data Loading Tuning? Data Loading Tuning can be performed as follows:Watch the ABAP code in transfer and update rules.Load Balance on different Servers. Indexes on Source Tables.Use fixed length files if the data is loaded from flat files

and put the file on the application server.Use the content extractor.Use PSA and data target in parallel option in the info

package. Start Several Info Packagers parallel with different

selection options. Buffer the SID number ranges if the data is loaded a lot

at once. Load Master Data before loading Transaction Data.

16. What is a data source?  The source which is sending data to a particular

info source on BW, for example it contains an OCUSTOMER_ATTR data source to supply attributes to OCUSTOMER from R/3.

17. What is an info source? Group of logically related objects, for example

the OCUSTOMER info source will contain data related to customer and attributes like customer number, address, phone no, etc.

18. Difference between display attributes and navigational attributes?

Display attribute is one, which is used only for display purpose in the report. Where as navigational attribute is used for drilling down in the report. We don't need to maintain Navigational attribute in the cube as a characteristic (that is the advantage) to drill down.

19. Why we delete the setup tables (LBWG) & fill them (OLI*BW)?

Initially we don't delete the setup tables but when we do change in extract structure we go for it. We r changing the extract structure right, that means there are some newly added fields in that which r not before. So to get the required data (i.e.; the data which is required is taken and to avoid redundancy) we delete n then fill the setup tables.  

To refresh the statistical data. The extraction set up reads the dataset that you want to process such as, customers orders with the tables like VBAK, VBAP) & fills the relevant communication structure with the data. The data is stored in cluster tables from where it is read when the initialization is run. It is important that during initialization phase, no one generates or modifies application data, at least until the tables can be set up.

20. What types of partitioning are there for BW?

There are two Partitioning Performance aspects for BW (Cube & PSA)

Query Data Retrieval Performance Improvement: Partitioning by (say) Date Range improves data

retrieval by making best use of database  execution plans and indexes (of say Oracle database engine).

Transactional Load Partitioning Improvement: Partitioning based on expected load volumes and

data element sizes. Improves data loading into PSA and Cubes by info packages (Eg. without timeouts).

21. How can compare data in R/3 with data in a BW Cube after the daily delta loads?

 

When go to R/3 TCode RSA3 and run the extractor. It will give you the number of records extracted. Then go to BW Monitor to check the number of records in the PSA and check to see if it is the same & also in the monitor header tab.

RSA3 is a simple extractor checker program that allows you to rule out extracts problems in R/3. It is simple to use, but only really tells you if the extractor works. Since records that get updated into Cubes/ODS structures are controlled by Update Rules, you will not be able to determine what is in the Cube compared to what is in the R/3 environment. You will need to compare records on a 1:1 basis against records in R/3 transactions for the functional area in question. I would recommend enlisting the help of the end user community to assist since they presumably know the data.

22. What is Dataflow in BW ? Data flows from transactional system to

analytical system (BW). Data Sources on the transactional system needs to be replicated on BW side and attached to info Source and update rules respectively.

23. Difference between info cube and ODS?

 Info cube is structured as star schema (extended) where a fact table is surrounded by different dim table that are linked with DIM'ids. And the data wise, you will have aggregated data in the cubes. No overwrite functionality

ODS is a flat structure (flat table) with no star schema concept and which will have granular data (detailed level). Overwrite functionality.

24. What is landscape of R/3 & what is landscape of BW ?

Then Landscape of R/3 have the development system, testing system, production system

Development system: All the implementation part is done in this sys. (I.e., Analysis of objects developing, modification etc) and from here the objects are transported to the testing system, but before transporting an initial test known as Unit testing (testing of objects) is done in the development sys.

Testing/Quality system: quality check is done in this system and integration testing is done.

Production system: All the extraction part takes place in this sys.

  

25. What is a source system? The source system is that which sends the data to

BW like R/3, flat file, oracle database or external systems.

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