SAP Basis

ADM100 Lesson: Architecture of Database Systems
Lesson:
132
Architecture of Database Systems
Lesson Duration: 45 minutes
Lesson Overview
This lesson provides basic theoretical information about the architecture
and functionality of a relational database.
Lesson Objectives
After completing this lesson, you will be able to:
• Describe in principle the structure and architecture of database
systems
You can use this figure to explain in principle the work of a database
system. All changes that are requested by the SAP system are performed
by the work processes using assigned database processes. Read accesses
are always made using the DB buffer. If this does not contain the requested
data, this data is read from the data tables and stored in the buffer. Access
to internal DB structure data may be required to find the data in the data
tables. Changing accesses are always recorded in the database log files,
usually using the intermediate layer of a “log buffer”. These logs are
essential to ensure the consistency of the database if a reset is necessary.
Business Example
SAP systems store the application data in a relational database. The
administrator regularly backs up this data.
Fundamentals of Database Administration
A database management system (DBMS) includes database processes, a
buffer in the main memory, data files that contain the data, and log files, in
which changes to the data are logged.
At the start of an SAP system, all work processes are linked to a database
process. Database queries are passed by SAP work processes to their
dedicated database processes, which perform the query on the database.
The data is stored in the data files: Access to the data always takes place
using the buffer in main memory.
The special database processes are responsible for the exchange of data
between the buffer and the data files. During this exchange, the data is
always read and written in complete pages (which usually contain several
data records).
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