Typical Parameter Settings for SAP Buffers 

Repository Buffers (nametab buffers)

Table definition buffer
(TTAB)

For the TTAB buffer, the size of the management part and the user data cannot be adjusted separately. Both are managed by the parameter rsdb/ntab/entrycount , which specifies the number of directory entries in the buffer. Each entry has a size of about 0.17 KB. This parameter also specifies the number of directory entries for the other three Repository buffers.

Field description buffer
(FTAB)

The number of directory entries is twice the number specified by the parameter rsdb/ntab/entrycount . Each entry requires about 0.039 KB in the management part of the buffer. The size of the data portion in KB is determined by rsdb/ntab/ftabsize .

Short nametab buffer
(SNTAB)

The number of directory entries is twice the number specified by the parameter rsdb/ntab/entrycount . Each entry requires about 0.039 KB in the management part of the buffer. The size of the data portion in KB is determined by rsdb/ntab/sntabsize .

Initial record buffer
(IRBD)

The number of directory entries is twice the number specified with the parameter rsdb/ntab/entrycount . Each entry requires about 0.039 KB in the management part of the buffer. The size of the data portion in KB is determined by rsdb/ntab/irbdsize .

 

The following table summarizes the buffer sizes that can be allocated, along with the corresponding profile parameters. It also contains the number of the pool containing the buffer:

Table: Buffer Capacity

Buffer

Management Header
(Size in KB)

User Data
(Size in KB)

Key

Pool

TTAB

0.17 KB ´ rsdb/ntab/entrycount

  

42

40

FTAB

0.039 KB ´ 2 ´ rsdb/ntab/entrycount

rsdb/ntab/ftabsize

43

40

SNTAB

0.039 KB ´ 2 ´ rsdb/ntab/entrycount

rsdb/ntab/sntabsize

45

40

IRBD

0.039 KB ´ 2 ´ rsdb/ntab/entrycount

rsdb/ntab/irbdsize

44

40

 

Thus, the size of the shared memory pool is controlled by the parameter ipc/shm_psize_40 . For more information, see Repository Buffers

Table Buffers

Generic key (resident) buffer (TABL)

The number of directory entries (one for each resident table or generic area) is specified by zcsa/db_max_buftab . The size of the data space in bytes is defined by zcsa/table_buffer_area . The placement of the buffer can be controlled with ipc/shm_psize_19 and is usually set to 10 (pool 10). The parameter zcsa/exchange_mode should not be changed. Keep its default value off.

Single key (partial) buffer (TABLP)

The number of directory entries (one per table) is specified by rtbb/max_tables . The size of the data space in KB is defined by rtbb/buffer_length . The placement of the buffer can be controlled with ipc/shm_psize_33 and is usually set to 0, which means that it is not in a pool. The parameter rtbb/frame_length specifies the size of one frame in KB and should always be kept at its default value of 4. For more information, see Table Buffers

Program Buffers

The size of the program buffer can only be specified by one parameter, abap/buffersize which defines the size in KB. The number of directory entries is calculated from this parameter. The placement of the buffer can be controlled with ipc/shm_psize_06 and is usually set to 0, which means that it is not in a pool. For more information, see Program Buffers.

SAPgui Buffers

Screen buffer (PRES)

The size of the directory, that is, the maximum number of screens is specified by zcsa/bufdir_entries . The total size of the buffer in KB is defined by zcsa/presentation_buffer_area , which includes the space for the directory.

Control the placement of the SAPgui buffers using parameter ipc/shm_psize_14 . This parameter is usually set to -10 , which means that it is in pool 10.

CUA buffer

The parameter rsdb/cua/buffersize defines the total size of the buffer in KB. The number of directory entries is calculated as: total size / 2KB . The placement of the buffer can be controlled with ipc/shm_psize_47 and is usually set to -40 , which means that it is in pool 40. For more information, see SAPgui Buffers.

Roll and Paging Buffers

The parameters rdisp/ROLL_SHM and rdisp/PG_SHM are used to allocate the roll and paging buffer in 8KB blocks.

This buffer is normally placed outside a pool. To place the buffer inside a pool, set the parameters ipc/shm_psize_08 and ipc/shm_psize_09 . For more information, see R/3 Roll and Paging Buffers.

SAP Calendar Buffer

The size of the calendar buffer in bytes is specified by the profile parameter zcsa/calendar_area . For more information, see SAP Calendar Buffer.

See also:

 

Note 103747 in SAPNet.

Special Aspects of Tuning

Call Statistics

Reasons for Poor Buffer Quality

Buffer Types