SAP HANA Architecture and Technology

SAP HANA Architecture and Technology

This blog gives a brief overview of the architecture of multitenant database containers.

Overview of Architecture and Technology

An SAP HANA system is a database management system (DBMS); that is, it is a server component that manages a database model. A Database system captures and analyzes information by interacting with the user, other applications, and the database itself. A general-purpose database management system permits the definition, creation, querying, update, and administration of databases.

A DBMS performs the following functions:
Manages massive amounts of data
Maintains relationships between data
Provides secure access to database wuth Authorization concept
Perform recovery of database to the most recent consistent status after a system failure
Delivers high performance for processing data requests

Database Terminology

A database is the collections of data , schema, tables , queries , reports ,views ,and other objects. Because the database is only a passive part of a database server, it requires some processes and memory structures to access the data and manage the database. The combination of processes and memory buffers is called a database instance.

Single-Container Versus Multiple-Container System

By Default SAP HANA 2.0 database system is install as a multiple-container system where as SAP HANA 1.0 database system is install as a single container database system.

A single-container system consists of one database that is managed by the SAP HANA database management system.

An SAP HANA system installed in multiple-container mode can contain more than one multitenant database container.

The concept of a multitenant database container system is based on a single SAP HANA system, or database management system, with a single system ID. This single system ID contains a minimum of one tenant database system and only one system database.

The system database keeps the system-wide landscape information, and provides system-wide configuration and monitoring. Users of 1 tenant cannot connect to other tenant. They also cannot access application data there, unless the system is enabled for cross database access. The tenant databases are, by default, isolated from each other in terms of application data and user management. Each tenant database system can be backed up and recovered independently from one another. Because all tenant databases are part of the same SAP HANA database management system, they all run with the same SAP HANA version (revision number). In addition, the defined high availability disaster recovery scenario applies to all tenant databases.

A multiple-container system has one system database, used for central system administration, and many multitenant database containers (including zero), also known as tenant databases. An SAP HANA system installed in multiple-container mode is identified by a single system ID (SID).

In a Multidatabase container (MDC) system, only name server run in system database. The name server contains landscape information about the system, including which tenant databases exist. It also provides indexserver functionality for the system database.

Below are the bullets points on MDC:

• Starting SAP HANA 1.0 SPS 09 (Revision 90), SAP HANA supports multitenant database containers in a single SAP HANA system. 
• Starting SAP HANA 2.0 SPS 01 (Revision 10), multitenant database containers will become the default 
• After HANA 2.0 SPS 01 installation is completed, only SYSTEMDB is created. Tenant DB's can be created from the SYSTEMDB using SQL 
• nameserver and other non-persistent services are available only on SYSTEMDB. 
• Indexserver and other persistent services are available only on tenant databases 
• In a multi-container database we connect to System DB happens through Nameserver which is act as SQL port. 
• there is no difference in tenant databases, which still uses the indexserver port for the connection. 
• by default with each instance you could have a maximum of 20 tenant databases. 
• Embedded statisticsserver run in both system DB(nameserver) and all tenant DB(Indexserver) 
• When SystemDB is down all tenant databases are also down. 
• We can restrict the memory allocation for specific tenant DB (global.ini --> [memorymanager] --> allocationlimit) 
• it is possible to configure statement memory limit per tenant. 
• Only a System DB user with DATABASE ADMIN system privilege can start/stop a tenant DB using SQL 
• Please note that tenant DB administrators cannot start/stop the tenant DB 
• In SAP HANA MDC the topology information is stored in index server, you can find this while performing backup. 
• The backup of a tenant will contain two files for indexserver one for topology and another for the data. 
• Configuration for the system database: As the nameserver takes over the role of the indexserver in system databases, recommendations for indexserver.ini have to be maintained in nameserver.ini.