Showing posts with label HANA Architecture. Show all posts

Interview Questions on SAP HANA Architecture

Top Answers to SAP HANA Interview Questions

Qs. Why SAP HANA is fast?

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Qs. Describe SAP HANA Database Architecture in brief.

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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.

Qs.What is ad hoc analysis?

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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.

Qs. What is SAP HANA?

SAP HANA is an in-memory database.

It is a combination of hardware and software made to process massive real time data using In-Memory computing.
It combines row-based, column-based database technology.
Data now resides in main-memory (RAM) and no longer on a hard disk.
It’s best suited for performing real-time analytics, and developing and deploying real-time applications.

An in-memory database means all the data is stored in the memory (RAM). This is no time wasted in loading the data from hard-disk to RAM or while processing keeping some data in RAM and temporary some data on disk. Everything is in-memory all the time, which gives the CPUs quick access to data for processing.

SAP HANA is equipped with multiengine query processing environment which supports relational as well as graphical and text data within same system. It provides features that support significant processing speed, handle huge data sizes and text mining capabilities.

To know more, check the article SAP HANA Introduction for Beginners

Qs. So is SAP making/selling the software or the hardware?

SAP has partnered with leading hardware vendors (HP, Fujitsu, IBM, Dell etc) to sell SAP certified hardware for HANA.
SAP is selling licenses and related services for the SAP HANA product which includes the SAP HANA database, SAP HANA Studio and other software to load data in the database.
To know more, check the article SAP HANA Hardware

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

The SAP HANA database is developed in C++.

Qs. 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.

Qs. Can I just increase the memory of my traditional Oracle database to 2TB and get similar performance?

NO.
You might have performance gains due to more memory available for your current Oracle/Microsoft/Teradata database but HANA is not just a database with bigger RAM.
It is a combination of a lot of hardware and software technologies. The way data is stored and processed by the In-Memory Computing Engine (IMCE) is the true differentiator. Having that data available in RAM is just the icing on the cake.

Qs. 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.

Following figure explains the difference between the two storage mechanism.

To know more, check the article Column Data Storage Vs Row Data Storage in HANA

NEXT>2

Multidimensional Expressions (MDX) is a query language for OLAP databases. Much like SQL, it is a query language for relational databases. It is also a calculation language, with syntax similar to spreadsheet formulas.

NOTE: OLAP tools enable users to analyze multidimensional data interactively from multiple perspectives.OLAP consists of three basic analytical operations:
1) consolidation (roll-up)
2) drill-down
3) slicing and dicing

1) Consolidation involves the aggregation of data that can be accumulated and computed in one or more dimensions.
For example, all sales offices are rolled up to the sales department or sales division to anticipate sales trends.

2) Drill-down is a technique that allows users to navigate through the details.
For example, users can view the sales by individual products that make up a region's sales.

3) Slicing and dicing is a feature whereby users can take out (slicing) a specific set of data of the OLAP cube and view (dicing) the slices from different viewpoints. These viewpoints are sometimes called dimensions.



MDX Video Tutorial

SAP HANA was initially, developed in Java and C++ and designed to run only Operating System Suse Linux Enterprise Server 11. SAP HANA system consists of multiple components that are responsible to emphasize computing power of HANA system.

Most important component of SAP HANA system is Index Server, which contains SQL/MDX processor to handle query statements for database. WHAT IS MDX

HANA system contains Name Server, Preprocessor Server, Statistics Server and XS engine, which is used to communicate and host small web applications and various other components.

Index Server

Index Server is heart of SAP HANA database system. It contains actual data and engines for processing that data. When SQL or MDX is fired for SAP HANA system, an Index Server takes care of all these requests and processes them. All HANA processing takes place in Index Server.

Index Server contains Data engines to handle all SQL/MDX statements that come to HANA database system. It also has Persistence Layer that is responsible for durability of HANA system and ensures HANA system is restored to most recent state when there is restart of system failure.

Index Server also has Session and Transaction Manager, which manage transactions and keep track of all running and closed transactions.

Index Server − Architecture

SQL/MDX Processor

It is responsible for processing SQL/MDX transactions with data engines responsible to run queries. It segments all query requests and direct them to correct engine for the performance Optimization.

It also ensures that all SQL/MDX requests are authorized and also provide error handling for efficient processing of these statements. It contains several engines and processors for query execution −

MDX (Multi Dimension Expression) is query language for OLAP systems like SQL is used for Relational database. MDX Engine is responsible to handle queries and manipulates multidimensional data stored in OLAP cubes.
Planning Engine is responsible to run planning operations within SAP HANA database.
Calculation Engine converts data into Calculation models to create logical execution plan to support parallel processing of statements.
Stored Procedure processor executes procedure calls for optimized processing; it converts OLAP cubes to HANA optimized cubes.

Transaction and Session Management

It is responsible to coordinate all database transactions and keep track of all running and closed transactions.

When a transaction is executed or failed, Transaction manager notifies relevant data engine to take necessary actions.

Session management component is responsible to initialize and manage sessions and connections for SAP HANA system using predefined session parameters.

Persistence Layer

It is responsible for durability and atomicity of transactions in HANA system. Persistence layer provides built in disaster recovery system for HANA database.

It ensures database is restored to most recent state and ensures that all the transactions are completed or undone in case of a system failure or restart.

It is also responsible to manage data and transaction logs and also contain data backup, log backup and configuration back of HANA system. Backups are stored as save points in the Data Volumes via a Save Point coordinator, which is normally set to take back every 5-10 minutes.

Preprocessor Server

Preprocessor Server in SAP HANA system is used for text data analysis.

Index Server uses preprocessor server for analyzing text data and extracting the information from text data when text search capabilities are used.

Name Server

NAME server contains System Landscape information of HANA system. In distributed environment, there are multiple nodes with each node has multiple CPU’s, Name server holds topology of HANA system and has information about all the running components and information is spread on all the components.

Topology of SAP HANA system is recorded here.
It decreases the time in re-indexing as it holds which data is on which server in distributed environment.

Statistical Server

This server checks and analyzes the health of all components in HANA system. Statistical Server is responsible for collecting the data related to system resources, their allocation and consumption of the resources and overall performance of HANA system.

It also provides historical data related to system performance for analyses purpose, to check and fix performance related issues in HANA system.

XS Engine

XS engine helps external Java and HTML based applications to access HANA system with help of XS client. As SAP HANA system contains a web server which can be used to host small JAVA/HTML based applications.

XS Engine transforms the persistence model stored in database into consumption model for clients exposed via HTTP/HTTPS.

SAP Host Agent

SAP Host agent should be installed on all the machines that are part of SAP HANA system Landscape. SAP Host agent is used by Software Update Manager SUM for installing automatic updates to all components of HANA system in distributed environment.

LM Structure

LM structure of SAP HANA system contains information about current installation details. This information is used by Software Update Manager to install automatic updates on HANA system components.

SAP Solution Manager (SAP SOLMAN) diagnostic Agent

This diagnostic agent provides all data to SAP Solution Manager to monitor SAP HANA system. This agent provides all the information about HANA database, which include database current state and general information.

It provides configuration details of HANA system when SAP SOLMAN is integrated with SAP HANA system.

SAP HANA Studio Repository

SAP HANA studio repository helps HANA developers to update current version of HANA studio to latest versions. Studio Repository holds the code which does this update.

Software Update Manager for SAP HANA

SAP Market Place is used to install updates for SAP systems. Software Update Manager for HANA system helps is update of HANA system from SAP Market place.

It is used for software downloads, customer messages, SAP Notes and requesting license keys for HANA system. It is also used to distribute HANA studio to end user’s systems.