What is SAP HANA for BASIS ?

What is SAP HANA?
SAP HANA is an exciting new technology brought to you by SAP. At its core it uses an innovative inmemory technique to store your data that is particularly suited for handling very large amounts of tabular, or relational, data with unprecedented performance. Common databases store tabular data row-wise, e. g. all data describing an address are stored adjacent to each other in memory. As long as your requirements are to access a single address your application will run quickly as all the required data is stored contiguously. However, consider the situation that your application requires a count of how many of the addresses stored relate to a particular country, city or ZIP code? In this case it would have to scan through the full table, select each row, and check for the country or city that is required. As all mass-storage devices, e. g. hard disks, access stored data in full blocks that can be quite large in comparison to the data of interest, e. g. 512 Bytes for a hard disk, it is likely that a mass-storage device has to read one or more rows just to check for a couple of characters, e. g. "Brazil" or "San Francisco". Tables of business data often contain many data fields, or columns, which are rarely used, e. g. data relating to other tables, or data fields controlling how other fields are to be used. Can you imagine the increase in efficiency if your application could just read around those unwanted fields and access the information that is really required?

If this style of data storage were used you would experience a significantly faster response from your database or application. SAP HANA allows you to read around unwanted data by organizing tables in this efficient columnar manner. In addition to the common row-oriented storage schema a columnoriented data storage layout can be used. This means your application does not have to wait for the database to fetch data that it does not need as all the data in a table column is stored in an adjacent manner. So, in our example of an address table, scanning through the country or city column is much faster than with row-oriented storage layout.

But what if your database system already caches all data in RAM, in fast accessible main memory close to the CPU? Would a column-oriented memory layout still speed access up? Measurements conducted at SAP and at the Hasso Plattner Institute in Potsdam have proven that reorganizing the data in memory column-wise brings a tremendous speed increase when accessing a subset of the data in each table row. As SAP HANA caches all data in memory, hard disks are rarely used in the system they are only needed to record changes to the database for permanent persistency. SAP HANA keeps the number of changes to your dataset as small as possible by recording every change as delta to your original dataset. Data is not modified in place but inserted or appended to a table column. This provides several advantages, not just speed of access. As all of the old data is retained, your applications can effectively “time-travel” through data providing views of the data as it has changed over time.

Contemporary database applications separate data management and applications in two distinct architectural layers, the database and application layer. This separation forces data to travel from the database to the application before it can be analyzed or modified. Sometimes very large amounts of data have to travel from one layer to another. SAP HANA avoids this common bottleneck by locating
data intensive application logic to where the data is, which is in the database itself. To enable this embedding of application logic in the database SAP has invented an extension to standard SQL




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