Contexts - Buffering Concept

The major difference between the context buffer and the normal database and table buffers is that it is only refreshed at given intervals. There is no attempt to update it synchronously, or even nearly synchronously. This means that it is not appropriate to use it for every context or context module.

Buffering Types

• Permanent (P): This is the default setting. In this case, the data is kept on each application server beyond the end of the transaction in which it is used. The buffer is reset every hour on the hour (8:00, 9:00...). Entries not found are not buffered. You can manually reset the buffer for each context using the Context Builder. The reset affects all application servers.

• Temporary (T): Data is only buffered for the duration of the current transaction.

• No buffering (N)

Buffer Size

You can set the maximum number of entries to be buffered. The default is 128. This number only applies to the permanent buffer for a single module. Within a transaction, all of the data that occurs is stored in the buffer unless you have switched off buffering for the module. It is usually best to leave the maximum buffer size set to 128. It is not often that a large number of key combinations occur within one hour on a single application server. Even if this does occur, you can expect combiniations from the first 128 entries to be repeated. The system resets the buffer after one hour, which should ensure that no one module monpolizes it.

Buffering Types

• An I buffer is a table that assigns derived values to the input fields of the module. It

• Only contains one entry with key values.

• An E buffer is a table that assigns the derived values of the module tot he key fields of the context, It

• contains more than one entry with key values.

• can be a join of all I buffers for the modules buffered

Performance

The E buffer gives the fastest access, since it can find the values requested in the DEMAND statement in a single step. Under certain circumstances, it can return a smaller number of hits than the I buffer.