SAP HANA: Interview Questions 101 through 110

101. How to add a system to the SAP HANA Studio?
  • Manually: With this method, you add one SAP HANA system at a time.
    • In the Systems view, right-click any blank area and choose Add system...
    • Fill in the server name, instance number and system description, and choose Next.
    • Fill in the user name and password, and choose Finish.
  • By importing a Landscape: This method allows you to connect to several SAP HANA systems at the same time, by importing an xml file generated previously by a landscape export from the SAP HANA Studio installed on your computer or another one.
    • Choose File → Import and choose SAP HANA → Landscape.
    • Specify the landscape file location, the destination folder for the import, and choose Finish.
    • Note: The landscape xml file does not contain any password. You will have to specify the user and password for any system added to the Systems view.
102. Explain the System View?
The Systems view lists all the systems that have been registered (manually, or by a landscape import).

  • Catalog: contains tables, views, indexes, etc, which are organized into schemas within packages.
  • Content: contains HANA-specific modeling objects
    • The physical tables are the only storage area for data within SAP HANA.
    • All the information models that will be created in the modeler will result in database views.
    • As such, SAP HANA does not persist redundant data for each model, and does not create materialized aggregates.
  • Provisioning: The Provisioning folder is essentially related to Smart Data Access, a data provisioning approach in which you can combine data from remote sources (Hadoop, SAP ASE, SAP IQ) with data of your SAP HANA physical tables, by exposing them as virtual tables.
  • Security: System administrator defines users and roles

  • 103. Where are the Column views located?
    The column views that you create are always located in schema _SYS_BIC, their metadata in schema _SYS_BI.
    If you run an SAP Application directly on SAP HANA, then the schema will always be SAP<SID_of _the_system>. For example, if your productive CRM System is called CRP, the corresponding schema will be SAPCRP.
    104. What are the SAP HANA Studio perspectives?
    • The SAP HANA Administration Perspective: is a main view to administer HANA systems.
      • Start and stop a system
      • Configure a system
      • Monitor a system
      • Backup and restore a system
      • Perform a problem analysis
    • The SAP HANA Modeler Perspectivecan create, manage, and transport information models (packages, information views, etc), define or extract data provisioning, configure the server, access SAP HANA documentation, etc.
    • The SAP HANA Development Perspective: Includes a development perspective with debugging functionality.
      • SAP HANA Extended Application Services (XS Server) is an application server, web server, and basis for an application development platform, that resides inside SAP HANA.
    105. What is a Delivery Unit in SAP HANA?
    Delivery unit is a single unit, which can be mapped to multiple packages and can be exported as single entity so that all the packages assigned to Delivery Unit can be treated as single unit.
    Users can use this option to export all the packages that make a delivery unit and the relevant objects contained in it to a HANA Server or to local Client location.
    The user should create Delivery Unit prior to using it.
    This can be done through HANA Modeler → Delivery Unit → Select System and Next → Create → Fill the details like Name, Version, etc. → OK → Add Packages to Delivery unit → Finish.
    106. Explain SAP HANA Engines?

    Run the Plan Visualization on your query to determine what engine is used to process a query. 


    • Join Engine:
      • Used when querying an Attribute View and also when running SQL script.
    • OLAP Engine:
      • Used for Analytic view (without calculated or derived columns).
    • Calculation Engine:
      • Used for Calculation views and Analytic views with calculated attributes
    107. What If I execute a standard ANSI92 SQL statement from a BI tool or in SAP HANA Studio. What engines will be used?
    Depends on what objects you reference in your query. If you're just querying plain base tables then the join engine will be used. As soon as you reference an analytic or calculation view, the other engines will be employed as well.
    108. If my Analytic View foundation is joined to attribute views, is both the OLAP and JOIN Engine used?
    Nope - during activation of the analytic views, the joins in the attribute views get 'flattened' and included in the analytic view run time object. Only the OLAP engine will be used then.
    109. Explain SAP HANA System Architecture?
    • The Index Server of the SAP HANA database is a core component that orchestrates the database's operations.
    • The Connection and Session Management which creates and manages sessions and connections for the database clients such as SAP BusinessObjects Reporting tools or applications.
    • The Transaction Manager coordinates transactions, controls transactional isolation, and keeps track of running and closed transactions.
    • Request Processing and Execution Control is a set of specialized engines and processors which handle the client requests are analyzed and executed.
    • SQL Processor receives the Incoming SQL requests and executes the Data Manaipulation Language (DML) statements - Insert, Select, Update, or Delete.
    • Metadata Manager handles Data Definition Lanaguage (DDL) statements, such as the definition of relational tables, columns, views, indexes and procedures.
    • Planning Engine handles Planning commands, wich allows financial planning apps to execute basic planning operations in the database layer.
    • Stored Procedure processor: handles procedure calls, which are written in SQLScript, a database programming language to execute application-specific calculations inside the database system.
    • MDX engine handles the Incoming MDX requests.
    • Calculation engine: Also handles the Incoming MDX requests, supports SQLScript, MD, and Planning operations.
    • Persistence layer component: manages the communication between the Index server and the File System that store the Data Volume and Transaction Log volume.
    • 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.
      • The new Statistics Server is also known as the embedded Statistics Server or Statistics Service.
      • The new Statistics Server is now embedded in the Index Server.
    110. How SAP HANA achieves High Availability and Disaster Recovery?
    • High Availability per DataCenter
      • High Availability configuration
        • N active servers in one cluster
        • M standby server(s) in one cluster
        • Shared file system for all servers
      • Services
        • Name and Index server on all nodes
        • Statistics server (only on one active server)
        • Name server active on Standby
      • Failover
        • Server X fails
        • Server N+1 reads indexes from shared storage and connects to logical connection of server X
    • SAP HANA Host Auto-Failover (Scale-Out with Standby)
      • High-Availability enables the failover of a node within one distributed SAP HANA appliance.
      • Failover uses a cold standby node and gets triggered automatically.
      • Landscape up to 3 master name-servers can be defined.
        • During startup one server gets elected as active master.
        • The active master assigns a volume to each starting index server or no volume in case of standby server.
      • Master name-server failure: In case of a master name-server failure, another of t he remaining name-servers will become active master.
      • Index-server failure: The master name-server detects an index-server failure and executes the failover. During the failover the master name-server assigns the volume of the failed index-server to the standby server.
    • Disaster Tolerance between DataCenters: SAP HANA provides SAP HANA Storage Replication and SAP HANA System Replication.
      • The mirroring is offered on the storage system level.
      • Performance impact is to be expected on data changing operations as soon as the synchronous mirroring is activated.
      • In case of emergency, the primary data center is not available any more and a process for the take-over must be initiated.
      • This take-over process then would end the mirroring officially, will mount the disks to the already installed HANA software and instances, and start up the secondary database side of the cluster. If the host names and instance names on both sides of the cluster are identical, no further steps with hdbrename are necessary.
      • Note: So far no hot standby via log shipping is available or even log shipping by recovering of log backups on a standby host.

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