User Guide

SAP AG November 2002

Naming

When names are assigned, we differentiate between standard backup media [Page 14 ]5 and

backup media for external backup tools [Page 145].

All SAP DB data is stored in structures called B* trees. The B* tree method is far more

efficient for accessing the rows of a table than other access methods (for example, sequential

scans).

A B* tree spans several levels from the root level at the top, to the index levels, through to

the lowest leaf level (one root level, n index levels (n>=1), one leaf level).

The storage units are called pages or data pages. SAP DB Version 7 supports a page size of

8 KB.

In SAP DB Version 7, all subsequent comparisons in a B* tree use ASCII code (each

character is assigned a numerical value between 0 and 255). The comparisons are performed

for all values on a character-by-character basis.

primary key [Page

10 ]1 .

B* Tree

The sort criterion for building a B* tree is the

Au Az Baf ... ... Bi

Waf

...

Aalen Amiens Anizy Athens Auber Avon

.. .. ..

Root level

Index level

Leaf level