Interview Questions & Answers

1. What is data integrity?
Data Integrity is about eliminating duplicate entries in the database. Data integrity means no duplicate data.

2. What is the difference between SAP BW 3.0B and SAP BW 3.1C, 3.5?
The best answer here is Business Content. There is additional Business Content provided with BW 3.1C that wasn't found in BW 3.0B. SAP has a pretty decent reference library on their Web site that documents that additional objects found with 3.1C.

 3. What is the difference between SAP BW 3.5 and 7.0?
SAP BW 7.0 is called SAP BI and is one of the components of SAP NetWeaver 2004s. There are many differences between them in areas like extraction, EDW, reporting, analysis administration and so forth. For a detailed description, please refer to the documentation given on help.sap.com. 

1. No Update rules or Transfer rules (Not mandatory in data flow)
2.Instead of update rules and Transfer rules new concept introduced called transformations.
3. New ODS introduced in additional to the Standard and transactional.
4. ODS is renamed as DataStore to meet with the global data warehousing standards.
And lot more changes in the functionalities of BEX query designer and WAD etc.
5. In Infosets now you can include Infocubes as well.
6. The Re-Modeling transaction helps you adding new key figures and characteristics and handles historical data as well without much hassle. This facility is available only for info cube.
7. The BI accelerator (for now only for infocubes) helps in reducing query run time by almost a factor of 10 - 100. This BI accl is a separate box and would cost more. Vendors for these would be HP or IBM.
8. The monitoring has been improved with a new portal based cockpit. Which means you would need to have an EP guy in your project for implementing the portal ! :)
9. Search functionality has improved!! You can search any object. Not like 3.5
10. Transformations are in and routines are passe! Yes, you can always revert to the old transactions too.

4. What is index?
Indices/Indexes are used to locate needed records in a database table quickly. BW uses two types of indices, B-tree indices for regular database tables and bitmap indices for fact tables and aggregate tables.

5. What is KPIs (Key Performance Indicators)?
(1) Predefined calculations that render summarized and/or aggregated information, which is useful in making strategic decisions.
(2) Also known as Performance Measure, Performance Metric measures. KPIs are put in place and visible to an organization to indicate the level of progress and status of change efforts in an organization.
KPIs are industry-recognized measurements on which to base critical business decisions.
In SAP BW, Business Content KPIs have been developed based upon input from customers, partners, and industry experts to ensure that they reflect best practices.

6. What is the use of process chain?

The use of Process Chain is to automate the data load process.
Used to automate all the processes including Data load and all Administrative Tasks like indices creation deletion, Cube compression etc.
Highly controlled data loading.

7. Difference between Display Attribute and Navigational Attribute?

The basic difference between the two is that navigational attributes can be used to drilldown in a Bex report whereas display attributes cannot be used so. A navigational attribute would function more or less like a characteristic within a cube.

To enable these features of a navigational attribute, the attribute needs to be made navigational in the cube apart from the master data info-object.

The only difference is that navigation attributes can be used for navigation in queries, like filtering, drill-down etc.
You can also use hierarchies on navigational attributes, as it is possible for characteristics.

But an extra feature is that there is a possibility to change your history. (Please look at the relevant time scenarios). If navigation attributes changes for a characteristic, it is changed for all records in the past.
Disadvantage is also a slow down in performance.

8. If there are duplicate data in Cubes, how would you fix it?
Delete the request ID, Fix data in PSA or ODS and re-load again from PSA / ODS.

9. What are the differences between ODS and Info Cube?
ODS holds transactional level data. It’s just as a flat table. It’s not based on multidimensional model. ODS have three tables
1. Active Data table (A table containing the active data)
2. Change log Table (Contains the change history for delta updating from the ODS Object into other data targets, such as ODS Objects or InfoCubes for example.)
3. Activation Queue table (For saving ODS data records that are to be updated but that have not yet been activated. The data is deleted after the records have been activated)

Whereas Cube holds aggregated data which is not as detailed as ODS. Cube is based on multidimensional model.

An ODS is a flat structure. It is just one table that contains all data.
Most of the time you use an ODS for line item data. Then you aggregate this data to an info cube

One major difference is the manner of data storage. In ODS, data is stored in flat tables. By flat I mean to say ordinary transparent table whereas in a CUBE, it composed of multiple tables arranged in a STAR SCHEMA joined by SIDs. The purpose is to do MULTI-DIMENSIONAL Reporting

In ODS; we can delete / overwrite the data load but in cube – only add is possible, no overwrite.

10. What is the use of change log table?

Change log is used for delta updates to the target; it stores all changes per request and updates the target.

11. Difference between InfoSet and Multiprovider

a) The operation in Multiprovider is "Union" where as in Infoset it is either "inner join" or "Outer join".

b) You can add Info-cube, ODS, Info-object in Multiprovider whereas in an Infoset you can only have ODS and Info-object.

c) An Infoset is an Info-provider that joins data from ODS and Info-objects( with master data). The join may be a outer join or a inner join. Whereas a Multiprovider is created on all types of Infoproviders - Cubes, ODS, Info-object. These InfoProviders are connected to one another by a union operation.

d) A union operation is used to combine the data from these objects into a MultiProvider. Here, the system constructs the union set of the data sets involved. In other words, all values of these data sets are combined. As a comparison: InfoSets are created using joins. These joins only combine values that appear in both tables. In contrast to a union, joins form the intersection of the tables.

12. What is the T.Code for Data Archival and what is it's advantage?
SARA.
Advantage: To minimize space, Query performance and Load performance

13. What are the Data Loading Tuning from R/3 to BW, FF to BW?

a) If you have enhanced an extractor, check your code in user exit RSAP0001 for expensive SQL statements, nested selects and rectify them.

b) Watch out the ABAP code in Transfer and Update Rules, this might slow down performance

c) If you have several extraction jobs running concurrently, there probably are not enough system resources to dedicate to any single extraction job. Make sure schedule this job judiciously.

d) If you have multiple application servers, try to do load balancing by distributing the load among different servers.

e) Build secondary indexes on the under lying tables of a DataSource to correspond to the fields in the selection criteria of the datasource. ( Indexes on Source tables)

f) Try to increase the number of parallel processes so that packages are extracted parallelly instead of sequentially. (Use PSA and Data Target in parallel option in the info package.)

g) Buffer the SID number ranges if you load lot of data at once.

h) Load master data before loading transaction data.

i) Use SAP Delivered extractors as much as possible.

j) If your source is not an SAP system but a flat file, make sure that this file is housed on the application server and not on the client machine. Files stored in an ASCII format are faster to load than those stored in a CSV format.

14. Performance monitoring and analysis tools in BW

a) System Trace: Transaction ST01 lets you do various levels of system trace such as authorization checks, SQL traces, table/buffer trace etc. It is a general Basis tool but can be leveraged for BW.

b) Workload Analysis: You use transaction code ST03

c) Database Performance Analysis: Transaction ST04 gives you all that you need to know about what’s happening at the database level.

d) Performance Analysis: Transaction ST05 enables you to do performance traces in different are as namely SQL trace, Enqueue trace, RFC trace and buffer trace.

e) BW Technical Content Analysis: SAP Standard Business Content 0BWTCT that needs to be activated. It contains several InfoCubes, ODS Objects and MultiProviders and contains a variety of performance related information.

f) BW Monitor: You can get to it independently of an InfoPackage by running transaction RSMO or via an InfoPackage. An important feature of this tool is the ability to retrieve important IDoc information.

g) ABAP Runtime Analysis Tool: Use transaction SE30 to do a runtime analysis of a transaction, program or function module. It is a very helpful tool if you know the program or routine that you suspect is causing a performance bottleneck.

15. Difference between Transfer Rules and Update Rules

a) Transfer Rules:
When we maintains the transfer structure and the communication structure, we use the transfer rules to determine how we want the transfer structure fields to be assigned to the communication structure InfoObjects. We can arrange for a 1:1 assignment. We can also fill InfoObjects using routines, formulas, or constants.
Update rules:
Update rules specify how the data (key figures, time characteristics, characteristics) is updated to data targets from the communication structure of an InfoSource. You are therefore connecting an InfoSource with a data target.

b) Transfer rules are linked to InfoSource, update rules are linked to InfoProvider (InfoCube, ODS).

i. Transfer rules are source system dependant whereas update rules are Data target dependant.

ii.The no. of transfer rules would be equal to the no. of source system for a data target.

iii.Transfer rules is mainly for data cleansing and data formatting whereas in the update rules you would write the business rules for your data target.

iv. Currency translations are possible in update rules.

c) Using transfer rules you can assign DataSource fields to corresponding InfoObjects of the InfoSource. Transfer rules give you possibility to cleanse data before it is loaded into BW.
Update rules describe how the data is updated into the InfoProvider from the communication structure of an InfoSource.
If you have several InfoCubes or ODS objects connected to one InfoSource you can for example adjust data according to them using update rules.

Only in Update Rules: a. You can use return tables in update rules which would split the incoming data package record into multiple ones. This is not possible in transfer rules.
b. Currency conversion is not possible in transfer rules.
c. If you have a key figure that is a calculated one using the base key figures you would do the calculation only in the update rules.

16. What is OSS?
OSS is Online support system runs by SAP to support the customers.
You can access this by entering OSS1 transaction or visit Service.SAP.Com and access it by providing the user name and password.

17. How to transport BW object?

Follow the steps.

i. RSA1 > Transport connection
ii. In the right window there is a category "all object according to type"
iii. Select required object you want to transport.
iv. Expand that object, there is select object, double click on this you will get the number of objects, select yours one.
v. Continue.
vi. Go with the selection, select all your required objects you want to transport.
vii. There is icon Transport Object (Truck Symbol).
viii. Click that, it will create one request, note it down this request.
ix. Go to Transport Organizer (T.code SE01).
x. In the display tab, enter the Request, and then go with display.
xi. Check your transport request whether contains the required objects or not, if not go with edit, if yes "Release" that request.

That’s it; your coordinator/Basis person will move this request to Quality or Production.

18. How to unlock objects in Transport Organizer?

To unlock a transport use Go to SE03 --> Request Task --> Unlock Objects

Enter your request and select unlock and execute. This will unlock the request.

19. What is InfoPackage Group?
An InfoPackage group is a collection of InfoPackages.

20. Differences Between Infopackage Groups and Process chains
i.Info Package Groups are used to group only Infopackages
where as Process chains are used to automate all the processes.

ii Infopackage goups:
Use to group all relevent infopackages in a group, (Automation of a group of infopackages only for dataload). Possible to Sequence the load in order.
Process Chains:
Used to automate all the processes including Dataload
and all Administrative Tasks like indices creation deletion, Cube compression etc
Highly controlled dataloading.

iii. InfoPackage Groups/Event Chains are older methods of scheduling/automation. Process Chains are newer and provide more capabilities. We can use ABAP programs and lot of additional features like ODS activation and sending emails to users based on success or failure of data loads.

21. What are the critical issues you faced and how did you solve it?

Find your own answer based on your experience.. 

22. What is Conversion Routine?

a) Conversion Routines are used to convert data types from internal format to external/display format or vice versa.

b) These are function modules.
c) There are many function modules, they will be of type
CONVERSION_EXIT_XXXX_INPUT, CONVERSION_EXIT_XXXX_OUTPUT.

example:

CONVERSION_EXIT_ALPHA_INPUT
CONVERSION_EXIT_ALPHA_OUTPUT

23. Difference between Start Routine and Conversion Routine
In the start routine you can modify data packages when data loading. Conversion routine usually refers to routines bound to InfoObjects (or data elements) for conversion of internal and display format.

24. What is the use of setup tables in LO extraction?

The use of setup table is to store your historical data in them before updating to the target system. Once you fill up the setup tables with the data, you need not to go to the application tables again and again which in turn will increase your system performance.

25. R/3 to ODS delta update is good but ODS to Cube delta is broken. How to fix it?
i. Check the Monitor (RSMO) what’s the error explanation. Based on explanation, we can check the reason

ii. Check the timings of delta load from R3 – ODS – CUBE if conflicting after ODS load

iii. Check the mapping of Transfer/Update Rules

iv. Fails in RFC connection

v. BW is not set as source system

vi. Dump (for a lot of reasons, full table space, time out, sql errors...)
Do not receive an IDOC correctly.

vii. There is a error load before the last one and so on...

26. What is short dump and how to rectify?
Short dump specifies that an ABAP runtime error has occurred and the error messages are written to the R/3 database tables. You can view the short dump through transaction ST22.
You get short dumps b'coz of runtime errors. The short dump u got is due to the termination of background job. This could be of many reasons.

You can check short dumps in T-code ST22. U can give the job tech name and your userid. It will show the status of jobs in the system. Here you can even analyze short dump. U can use ST22 in both R/3 and BW.

OR To call an analysis method,
choose Tools --> ABAP Workbench --> Test --> Dump-Analysis from the SAP Easy Access menu.
In the initial screen, you must specify whether you want to view today’s dump or the dump from yesterday. If these selection criteria are too imprecise, you can enter more specific criteria. To do this, choose Goto --> Select Short Dump
You can display a list of all ABAP dumps by choosing Edit --> Display List. You can then display and analyze a selected dump. To do this, choose Short Dump --> Dump Analysis.