This tutorial gives you an overview and talks about the fundamentals of SAP HANA Administration.
>> An SAP HANA system comprises all the server components of an installation of SAP HANA
>> An SAP HANA system consists of several servers, the most important of which is the index server. The index server contains the actual data stores and the engines for processing the data.
>> A multiple-host or distributed SAP HANA system is a system that is installed on more than one host. Otherwise, it is a single-host system. A host is a machine (comprised of CPU, memory, storage, network, and operating system) that runs parts of the SAP HANA system.
>> An SAP HANA instance is the set of server components of a distributed system that are installed on one host. The following figure shows a distributed system with three hosts, which each run a name server, index server, and so on.
>> SAP HANA supports multiple isolated databases in a single SAP HANA system. These are referred to as multitenant database containers.
>> An SAP HANA system installed on multiple hosts is identified by a single system ID (SID). It is perceived as one unit from the perspective of the administrator, who can install, update, start up, shut down, or backup the system as a whole. The different server components of the system share the same metadata and requests from client applications can be transparently dispatched to different servers in the system.
>> A multiple-container system always has exactly one system database and any number of multitenant database containers (including zero), also called tenant databases.
>> In a multiple-container system, only the system database runs the name server. The name server contains landscape information about the system as a whole, including which tenant databases exist. It also provides indexserver functionality for the system database. Unlike the name server in a single-container system, the name server of the system database in a multiple-container system does not own topology information, that is, information about the location of tables and table partitions in databases. Database-related topology information is stored in the relevant tenant database catalog.
SAP HANA Administration Availability And Scalability
>> Hana supports recovery measures ranging from faults and software errors, to disasters that decommission an entire data center. High availability is the name given to a set of techniques, engineering practices and design principles that support the goal of business continuity.
>> High availability is achieved by eliminating single points of failure (fault tolerance), and providing the ability to rapidly resume operations after a system outage with minimal business loss (fault resilience). Fault recovery is the process of recovering and resuming operations after an outage due to a fault. Disaster recovery is the process of recovering operations after an outage due to a prolonged data center or site failure. Preparing for disasters may require backing up data across longer distances, and may thus be more complex and costly.
>> The key to achieving high availability is redundancy, including hardware redundancy, network redundancy and data center redundancy. SAP HANA provides several levels of defense against failure-related outages:
>> Hardware Redundancy – SAP HANA appliance vendors offer multiple layers of redundant hardware, software and network components, such as redundant power supplies and fans, enterprise grade error-correcting memories, fully redundant network switches and routers, and uninterrupted power supply (UPS). Disk storage systems use batteries to guarantee writing even in the presence of power failure, and use striping and mirroring to provide redundancy for automatic recovery from disk failures. Generally speaking, all these redundancy solutions are transparent to SAP HANA’s operation, but they form part of the defense against system outage due to single component failures.
>> Software – SAP HANA is based on SUSE Linux Enterprise 11 for SAP and includes security pre-configurations (for example, minimal network services). Additionally, the SAP HANA system software also includes a watchdog function, which automatically restarts configured services (index server, name server, and so on), in case of detected stoppage (killed or crashed).
>> Persistence – SAP HANA persists transaction logs, save-points and snapshots to support system restart and recovery from host failures, with minimal delay and without loss of data.
>> Standby and Failover – Separate, dedicated standby hosts are used for failover, in case of failure of the primary, active hosts. This improves the availability by significantly reducing the recovery time from an outage.
Fore more information about SAP HANA, please refer HTTP://HANA.SAP.COM/ABOUTHANA.HTML
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