ARTICLE
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 foun
d 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 rare
that a large number of key combinations occur within one hour on a
single application server. Even if this does occur, you can expect
combinations from the first 128 entries to be repeated. The system
resets the buffer after one hour. The maximum of 128 should ensure that
no one module monopolizes 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 to
the 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.
Documentation extract taken from SAP system, � Copyright SAP AG. All rights reserved