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Function documentation Table Buffer  Locate the document in its SAP Library structure

Use

The table buffer is located between the application and the database. Its goal is to cache portions of a database table in the application server to reduce database load and network communication. As you can see in the following figure, each server process of the J2EE Engine contains its own table buffer instance, which is shared among all threads of the server. Changes made to buffered data within one server process should be propagated to all other nodes to avoid inconsistencies in the remote buffers. The buffer synchronization mechanism used in the J2EE Engine guarantees that changes to buffered data are propagated to all remote buffers with a short delay.

 

This graphic is explained in the accompanying text

The table buffer in a cluster of servers.  Each cluster node has its own table buffer.

Activities

Using the Java Dictionary, you can enable buffering for individual tables. To buffer a table, you must have defined its primary key. Furthermore, you can define the buffer granularity by specifying the primary key columns that form the table’s generic buffer key. The data units that are stored in the buffer are called generic buffer areas. Buffering is transparent to the application program.

The first buffer access implicitly loads the data into the buffer so that a subsequent request can retrieve the data from the table buffer, rather than having to access the database. When a query is issued against a buffered table, the system checks if the query’s WHERE clause restricts the result set to a generic buffer area with respect to the generic key defined in this table. If this is the case, the query is issued against the table buffer instead of the database. If the respective generic buffer area is not yet in the buffer, then it is loaded into the buffer before the query is processed.

You can view statistics about the use of the table buffer in the runtime tab of Monitoring Service in the Visual Administrator.

More information about the monitored data: Table Buffers Monitor

More Information

Buffer Granularity

Statements Using the Buffer

Statements Bypassing the Buffer

Modifications and actions on the remote buffers

Buffering Hints

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