I am going to cover SAP Hana from an database administrators point of view, I am not going to go into great depth and leave you with the various books and online courses, but explain enough for you to get up and running and have a play around with the Hana database, I will not be covering any S4 applications and will only focus on the database.
In a nutshell the SAP Hana system comprises of a number of components
- Index Server - the database itself
- XS Server - developer/admin tools
- Further Components -
There are a number of terminologies that you need to be aware in SAP Hana
- Instance - like in other database the instance is the processes and memory that access the Hana database
- System - is the physical or virtual machine that runs the processes, memory and database
- Node - is a single server that runs a Hana database when used in a distributed setup
- Distributed System - a collection of Hana nodes running SAP Hana to improve performance, scalability and availability.
The SAP Hana base is very similar to other databases, it consists of a network layer, processing layer (cpu and memory), persistenance layer (physical disks or SAN). The main difference is that Hana is a in memory database, which means that that the main data is held in memory (istead of on the disks), basically all tables reside in the servers memory and thus you need a server with large amounts of memory which today is not that expensive. So when deciding to use SAP Hana you need to consider what type of server (or Virtual Machine) you can use and if it will support the large amount of memory required of course depending on the size of your database. The persistence layer is used to store the non-volatile data during power outages, again this needs to be large enough to stopre all the data. SAP Hana uses transaction logs like other databases to store changes and thus can be used when unsuspecting outages occur. Now days as SSD's disks are cheap you can have data and logs stored on both generally using s SAN. SAP Hana supports both 1GB and 10GB networks, depending on your requirements you will configure one of them.
SAP Hana supports either SUSE or RedHat Linux you should see the SAP website on what version support which version on Hana.
There are a number of processes that you should be aware of which can be categorized below
| System Start | start service, HDB daemon |
| Core Procceses | index server, name server, XS server, web dispatcher, compile server, preprocessor, statistics server, script server |
| Auxiliary Processes | lifecycle manager, hdb*-processes, Hana studio/client |
| Other Auxiliary Processes | host control, SMD agent, 3rd party tools |
When you start SAP Hana system a single process starts everything which is called HDB daemon, this process starts the database processes and keeps them running (will automatically restart them if needed), and to start the SAP web dispatcher process and is used by many tools to interact with the Hana database.
- Index Server - is the database process, it provides the SQL interface into the database, manages tables and other database objects and processes SQL queries, this process will have a large memory footprint.
- Name Server - Hana uses a topology to obtain a view of itself, this is the name server, it hosts the backup manager and is important when using distributed systems
- XS Server/Web Dispatcher - XS server is used by the developer tools such as javascript, OData services and XMLA, HTML5, you can then use the web dispatcher to expose HTTP.
- Compile Server - performs the compilation of stored procedures and programs, for example, SQLScript procedures.
- Preprocessor - creates searchable, full-text indexes, normalization within the database.
- Statistic Server - is responsible for collecting the data related to system resources, their allocation, and consumption of the resources and overall performance of HANA system.
- Script Server - is used by the Application Function Library and thus is optional.
- Lifecycle Manager - used to update the database and various components, it uses a GUI and can even support complete system landscapes.
- HDB* Tools - hdblcm/hdblcmgui used to update the database, hdbsql is a commandline SQL tool, hdbuserstore for storing users/passwords
- SAP Hana Studio/Client - an application used to administer the Hana database
Sizing a SAP Hana system depends on your requirements, in most cases you will probably will be using as S4/Hana system, you need to first identify the size of the database which will thus identify you RAMrequirements, making sure that the platform you use can cope now and in the future accounting for any growth. Most companies now are turning to either SAP Cloud, Azure or AWS which are all fully supported by SAP. Its probably best to get a SAP vendor involved to help you deciding the platform of choice. You do have the option to have a on-prem system but make sure that any hardware is fully supported by SAP, use the SAP matrix to help you decide.