SAP HANA: Interview Questions 31 through 40

31. What is the language SAP HANA is developed in? 

The SAP HANA database is developed in C++.  

32.What is the operating system supported by HANA? 

Currently SUSE Linux Enterprise Server x86-64 (SLES) 11 SP1 is the Operating System supported by SAP HANA.  

33. 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. 

34. What are the advantages and disadvantages of row-based tables? 

• Advantages: 

• The application needs to only process a single record at one time (many selects and/or updates of single records). 

• The application typically needs to access a complete record (or row). 

• Neither aggregations nor fast searching are required. 

• The table has a small number of rows (e. g. configuration tables, system tables). 

• Disadvantages: 

• In case of analytic applications where aggregation are used and fast search and processing is required. In row based tables all data in a row has to be read even though the requirement may be to access data from a few columns. 

  35. Why materialized aggregates are not required in HANA? 

Since the SAP HANA database resides entirely in-memory all the time, additional complex calculations, functions and data-intensive operations can happen on the data directly in the database.  

Hence materialized aggregations are not required.  

36. What is ad-hoc analysis? 

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. 

37. Describe SAP HANA Database Architecture in brief.  
The SAP HANA database is developed in C++ and runs on SUSE Linux Enterpise Server.  

SAP HANA database consists of multiple servers and the most important component is the Index Server.  

SAP HANA database consists of Index Server, Name Server, Statistics Server, Preprocessor Server and XS Engine.    

Index Server: 

• Index server is the main SAP HANA database component 

• It contains the actual data stores and the engines for processing the data. 

• The index server processes incoming SQL or MDX statements in the context of authenticated sessions and transactions. 

Persistence Layer: 

• The database persistence layer is responsible for durability and atomicity of transactions. It ensures that the database can be restored to the most recent committed state after a restart and that transactions are either completely executed or completely undone. 

 Preprocessor Server: 

• The index server uses the preprocessor server for analyzing text data and extracting the information on which the text search capabilities are based. 

 Name Server: 

• The name server owns the information about the topology of SAP HANA system. In a distributed system, the name server knows where the components are running and which data is located on which server. 

 Statistic Server: 

• The statistics server collects information about status, performance and resource consumption from the other servers in the system.. The statistics server also provides a history of measurement data for further analysis. 

 Session and Transaction Manager: 

• The Transaction manager coordinates database transactions, and keeps track of running and closed transactions. When a transaction is committed or rolled back, the transaction manager informs the involved storage engines about this event so they can execute necessary actions. 

 XS Engine: 

• XS Engine is an optional component. Using XS Engine clients can connect to SAP HANA database to fetch data via HTTP. 

38. What are the types of modeling views in HANA? 

There are 3 types of modeling in HANA: 

• Attribute View 

• Analytic View 

• Calculation View 

 39. What is a Delivery Unit? 

A delivery unit could be regarded as a collection of several packages, used for transporting content from one HANA system to another.   
Delivery unit (DU) is a container used by the Life Cycle Manager (LCM) to transport repository objects.  

40. There are 2 types of packages in content. What are they? 

In HANA, 2 types of packages can be created. 

• Structural: Package only contains sub-packages. It cannot contain repository objects. 

• Non-Structural: Package contains both repository objects and sub-packages. 

By default it creates Non-structural.