SAP HANA database


SAP HANA database

The heart of the SAP HANA database is the relational database engines. There are two engines within the SAP HANA database:

- The column-based store, storing relational data in columns, optimized holding tables with
huge amounts of data, which are aggregated and used in analytical operations.
- The row-based store, storing relational data in rows, as traditional database systems do.

This row store is more optimized for write operation and has a lower compression rate, and query performance is much lower compared to the column-based store.

The engine used to store data can be selected on a per-table basis at the time of creation of a table. Tables in the row-store are loaded at startup time, whereas tables in the column-store can be either loaded at startup or on demand, during normal operation of the SAP HANA database.
Both engines share a common persistency layer, which provides data persistency consistent across both engines. There is page management and logging, much like in traditional databases.
Changes to in-memory database pages are persisted through savepoints written to the data volumes on persistent storage, which is usually hard drives. Every transaction committed in the SAP HANA database is persisted by the logger of the persistency layer in a log entry written to the log volumes on persistent storage. The log volumes use flash technology storage for high I/O performance and low latency.
The relational engines can be accessed through a variety of interfaces.
The SAP HANA database supports SQL (JDBC/ODBC), MDX (ODBO), and BICS (SQL DBC). The calculation engine allows calculations to be performed in the database, without moving the data into the application layer. It also includes a business functions library that can be called by applications to do business calculations close to the data.
The SAP HANA-specific SQL  Script language as an extension to SQL that can be used to push down data-intensive application logic into the SAP HANA database.


Sap Hana Architecture

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