7/21/2019 2103827 - Profile Parameters for Table Buffer as of SAP Kernel Release 7.40

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SAP Note 

Header Data

Symptom 

With SAP Kernel Release 7.40, significant parts of the table buffer were reimplemented. New profile parameters have been introduced for thedimensioning of the new table buffer. Their meaning is explained in this SAP Note.

Other Terms 

Table buffer rsdb/tbi_buffer_area_MB rsdb/tbi_dir_entries ST02 AL12 

Reason and Prerequisites 

Up to SAP Kernel Release 7.2x, there were two separate buffer instances - the single record buffer and the generic table (key) buffer. With SAPKernel Release 7.40, these two buffer instances have been replaced by a single table buffer in which both single record and generically bufferedtables are managed. With regard to the functions visible from the outside, the new table buffer does not differ significantly from the old bufferinstances; however, memory management has been switched to the code basis of internal tables to enable more flexible responses to newrequirements. A direct benefit of this switch is that secondary instances are now also supported in the buffer, which means that accesses usingsecondary keys are now considerably more efficient than in the old buffer implementation.

New profile parameters have also been introduced with the new buffer implementation; you can use them to dimension the table buffer.

Solution 

Until SAP Kernel Release 7.2x, the memory layout of the two buffer instances was controlled using two pairs of profile parameters (for moreinformation about these parameters, see SAP Note 480710):

 As of SAP Kernel Release 7.40, the table buffer is controlled by two profile parameters only: 

The two parameters are delivered with these default values:

To prevent the loss of the old buffer settings following an upgrade from an earlier kernel release to a kernel release of 7.40 or above, the followingcompatibility rule has been implemented:

If the new parameters are not set in the profile or if they have the specified default values there, and if the old parameters are still set in the profile,then the actual parameter values for the new table buffer are calculated as follows from the old parameter values:

In all other cases - particularly if the new parameters have been set in the profile with values other than the default values - the buffer is dimensionedin accordance with the new parameters.

This means that if you now want to make changes to the dimensioning of the new table buffer, you must include the parametersrsdb/tbi_dir_entries and  rsdb/tbi_buffer_area_MB in the profile with the desired values and remove the old buffer parameters. The latter actionis not absolutely necessary but it does prevent possible confusion and misunderstandings.

2103827 - Profile parameters for table buffer as of SAP Kernel Release 7.40 

Version  1 Validity: 02.12.2014 - active Language  English

Released On  03.12.2014 13:41:03

Release Status Released for Customer

Component  BC-DB-DBI DB Independent Database Interface

Priority  Correction with medium priorityCategory  FAQ

Generic table buffer zcsa/db_max_buftab Number of tables or generic areas (directories) that can be buffered

zcsa/table_buffer_area Area allocated to the buffer instance in the shared memory in bytes

Single record buffer rtbb/max_tables Number of tables (directories) that can be buffered

rtbb/buffer_length  Area allocated to the buffer instance in the shared memory in kilobytes

New table buffer rsdb/tbi_dir_entries Number of tables or generic areas (directories) that can be buffered

rsdb/tbi_buffer_area_MB  Allocated area in the shared memory in megabytes

rsdb/tbi_dir_entries = 100

rsdb/tbi_buffer_area_MB = 1

rsdb/tbi_dir_entries zcsa/db_max_buftab + rtbb/max_tablesrsdb/tbi_buffer_area_MB ((zcsa/table_buffer_area + rtbb/buffer_length * 1024) * 1.1) / (1024*1024)

7/21/2019 2103827 - Profile Parameters for Table Buffer as of SAP Kernel Release 7.40

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Note that depending on the support package level of the 7.40 basis system, the old buffer parameters might still be specified in transaction ST02.For more information, see SAP Note 1864189.

Validity

References

This document refers to:

SAP Notes 

This document is referenced by:

SAP Notes (1) 

Software Component From Rel. To Rel. And Subsequent

KRNL64NUC  7.40  7.40  

KRNL64UC  7.40  7.40  

KERNEL  7.40  7.40  

1864189 Incorrect display of Generic Key and Single Record Buffer in ST02 

480710 Profile parameters for table buffers (for SAP Kernel Release 7.2x and below) 

480710 Profile parameters for table buffers (for SAP Kernel Release 7.2x and below)