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Background documentation Buffer Granularity  Locate the document in its SAP Library structure

Table buffering can be activated in the Java Dictionary table editor by setting the table buffer attribute and specifying the buffer granularity. The granularity is the number of primary key columns that determines the key range of the table to be buffered – that is, the set of rows whose first N key columns have equal values. The graphic below depicts the different buffering options with respect to buffer granularity:

      Full buffering (N = 0)

The complete table is buffered – that is, the content of the whole table is loaded into the buffer upon first access to any data from the table.

      Generic buffering (0 < N < # primary key columns)

A generic (buffer) key (first N key fields) is specified. This generic key divides the contents of the table into the so-called generic areas. When accessing any data with a specified generic key, the whole generic area is loaded into the buffer. The figure shows the case of generic buffering with one and two fields as generic key.

      Single records buffering (N = # primary key columns)

Single rows are buffered. Only single rows are read from the database and stored in the buffer.

 

Negative information (non-existent rows) is also stored for each type of buffer granularity. In the case of full buffering, the buffer stores the whole table and therefore knows which rows do not exist. In the case of buffering generic areas and single rows, this information is stored explicitly: each generic not found area is entered into the buffer and each key of a not found row is buffered explicitly.

 

This graphic is explained in the accompanying text

The buffer granularity determines the buffered key range. N = 3: all fields - single row buffering; N  = 2: generic buffering with 2 key fields; N  = 1: generic buffering with 1 key field; N = 0: full buffering.

More Information

Buffering Type

Buffering Hints

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