The fact that each application server has its own buffers could result in data inconsistency across the various application servers (instances). To prevent data inconsistency, the SAP System uses periodical buffer synchronization, which is sometimes called buffer refresh.
Every modifying action on buffered data, which could also be buffered by other application servers, produces synchronization telegrams that are written to a central DB table (DDLOG). Every application server periodically reads the telegrams written since the last synchronization, and checks its buffers for data to be refreshed.
Buffer synchronization can be controlled by changing the following parameters in theinstance profile:
During the period between two refreshes, an application server may read data from its buffers while they are being modified by another application server. For this reason, no important volatile customer data should be buffered in the SAP buffers.
Examples of buffered data:
Buffer synchronization is required only for distributed SAP Systems when more than one application server (instance) is used. If your SAP System utilizes only one application server (instance), buffer synchronization is not needed. When the application server is restarted, all buffers are erased and dynamically reconstructed.
Before you usetp (SAP transport program) to import objects into a central instance (that is, only one instance in the whole SAP System), you should set the following parameter:
If you set the paramter to ‘exeoff ’, the central instance does not read the DDLOG table. This means that any changes to repository objects in the database (that is written to using tp ) are not updated in the SAP repository buffers. This may mean that the system displays syntax error messages for the ABAP programs that are affected.
The ABAP processor can detect whether a version of the ABAP program imported viatp is new, and reloads the program buffer. The SAP repository buffers still contain the old repository objects.
R/3 Repository Buffers (Nametab Buffers) Buffer Types