SAP Note 14754 - Profile parameters for buffer synchronization

Symptom:

You want to know more about profile parameters of buffer synchronization. The general function of buffer synchronization is explained in Note 36283. You must read this note first.

Reason and Prerequisites

Documentation is missing or unclear.

Solution
The buffer synchronization is basically controlled by two instance profile parameters:

1) rdisp/bufrefmode
This parameter defines (a) if synchronization records are written to the table DDLOG (possible values "sendon" or "sendoff") and (b) if the periodic buffer invalidation occurs (possible values "exeauto" or "exeoff").

In a system with several instances (central instance and at least one additional application server), the parameter must be set as follows on ALL instances, including the central instance:
rdisp/bufrefmode = sendon,exeauto

In a system that has only the central instance, you can deactivate the writing of DDLOG entries:
rdisp/bufrefmode = sendoff,exeauto
However, you must ensure that you reset the setting on the central instance to "sendon,exeauto" when you add at least one additional application server to avoid data inconsistencies in buffered objects.

Buffer invalidation (exeauto) should always be set so that changes to buffered objects that arrive in the system by transports are also synchronized. The setting exeoff is permitted only for test purposes.

2) rdisp/bufreftime
This parameter defines the time interval in which the buffer invalidation is executed. The unit is seconds, the default value is 120. This default value should only be changed in exceptional circumstances, and only after consultation with SAP.


Automatic correction of the parameter rdisp/bufrefmode by the system
Since the parameter rdisp/bufrefmode was frequently set incorrectly (for example, because it was forgotten to change the parameter value from "sendoff" to "sendon" after adding an additional application server to the central instance) the kernel patches below change the system behavior in such a way that the system switches to "sendon" mode independently of the parameter rdisp/bufrefmode as soon as the system detects at least two instances that are connected to the system.

Furthermore, the periodic evaluation of the DDLOG entries is now always active ("exeauto" mode) and you can no longer deactivate it by setting the rdisp/bufrefmode parameter to "exeoff". This excludes any possible buffer inconsistencies that may occur as a result of the transports.

These changes are effective for the Basis Releases 6.x and 7.00 as of the following kernel patches and for all higher releases (further information is available in Note 1054534):

6.40: 185
7.00: 110

Other terms

rdisp/bufrefmode, rdisp/bufreftime