8/10/2019 36283 - Buffer dfSynchronization

http://slidepdf.com/reader/full/36283-buffer-dfsynchronization 1/2

SAP Note

Header Data

Symptom

Introductory remarks:Buffer synchronization makes sure that application servers are informed about changes to bufferedtables or other buffered objects that were made on other application servers or using transporttools. For technical realization, the change operations are stored in Table DDLOG. On eachapplication server, a process is run periodically to read the current change requests from TableDDLOG and inform the local buffers.

Therefore buffer synchronization is carried out at a delay. The period is controlled using profileparameter rdisp/bufreftime. For performance reasons, the value should never be set to less than 60seconds. If modifications to tables need to be apparent on the application servers in a shorterperiod of time, those tables must either not be buffered, or BYPASSING BUFFER has to be added tocritical read operations.

Central systems are a special case. Here, changes to buffered objects can only be made usingtransport tools. For this reason, it does not make sense to log changes to the application serveritself in table DDLOG. To prevent this, the profile parameter rdisp/bufrefmode in the central system(and only there) must contain the value "sendoff,exeauto". See also Note 14754.

There are general and specific error symptoms.

General error symptoms

l Modifications to table contents are apparently not carried out.

l Access to buffered objects yield different results on different application servers.

Specific error symptoms

l Error message BY4 in the syslog: SQL error x occurred during INSERT DDLOG.

Other Terms

Reason and Prerequisites

According to the buffer synchronization mechanism, there are two problem zones: the writing to tableDDLOG and the periodic buffer invalidation.

Known causes

1. There is more than one application server and on (at least) one of them profile parameterrdisp/bufrefmode is set to "sendoff,exeauto".

2. INSERT DDLOG produces a database error.

3. For database platforms Oracle and SAP DB only: The R/3 system was built incorrectly. Insteadof using R/3 tools, the system was created using a database copy from another R/3 system and,before start-up, Table DDLOG was not checked to make sure that it did not contain any records.In such a case, buffer invalidation is generally not carried out.

4. Only for database platform DB2: For testing reasons, the date was set to a future date on theapplication server. This means that DDLOG entries are written with a time stamp in the future.In this case, there is actually no buffer invalidation.

Solution Program RSDBBUFF is available as an analysis tool. It can be used, for example, to view the DDLOGand buffer contents.

re. cause 1: On all application servers (including the central instance!), profile parameterrdisp/bufrefmode must be set to "sendon ,exeauto".

re. cause 2: The database error must be corrected. In the case of error message ORA-2289, see Note185821.

36283 - Buffer synchronization

Version 17 Validity: 28.01.2005 - active Language English

Released On 04.02.2005 15:38:10Release Status Released for CustomerComponent BC-DB-DBI DB Independent Database Interface

Priority Recommendations / Additional InfoCategory Consulting

8/10/2019 36283 - Buffer dfSynchronization

http://slidepdf.com/reader/full/36283-buffer-dfsynchronization 2/2

re. cause 3: All application servers must be stopped. Then all records in the table DDLOG must bedeleted using the appropriate database tool (in Oracle, for example, use the command TRUNCATE TABLEDDLOG) before the R/3 system can start operating again.

re cause 4: The DDLOG records with time stamps that are in the future must be deleted.

Validity

Support Packages & Patches

References

This document refers to:

SAP Notes

This document is referenced by:

SAP Notes (11)

Software Component From Rel. To Rel. And SubsequentSAP_BASIS 46A 46D

610 640

700 701

710 711

Support Packages

Software Component Release Support PackageSAP_BASIS 46C SAPKB46C41

46D SAPKB46D30

1054534 Automatic corrections for buffer synchronization parameters 1011158 Table buffering on a SAP instance.

841938 DB2/DB4/DB6: Buffer synchronisation between dw, tp & R3trans 815054 SU01: Problems when buffering table USR02 706478 Preventing Basis tables from increasing considerably 185821 ORA-2289 during insert on DDLOG

67211 Inconsistencies after program or DDIC changes 47239 Behavior of the table buffers 45456 Synchronization in transport: Overview (3.0/3.1) 14754 Profile parameters for buffer synchronization

1011158 Table buffering on a SAP instance. 1054534 Automatic corrections for buffer synchronization parameters 523129 Incorrect selection values from TVARV 841938 DB2/DB4/DB6: Buffer synchronisation between dw, tp & R3trans 706478 Preventing Basis tables from increasing considerably

815054 SU01: Problems when buffering table USR02 45456 Synchronization in transport: Overview (3.0/3.1) 67211 Inconsistencies after program or DDIC changes 14754 Profile parameters for buffer synchronization 185821 ORA-2289 during insert on DDLOG 47239 Behavior of the table buffers