sap Note 12948 - Significance of the roll area parameters

Symptom:

What is the meaning of the roll area parameters?

Solution

*** Warning ***
The profile parameters are critical and should only be modified by experts. Inadvertent changes may render the system unusable. To examine and improve system performance, please contact the Early Watch Service.
***************

There are three main parameters that define the roll area.
The following values are typical for Release 2.1D and 128 MB RAM:

• ztta/roll_area : Roll area per work process (memory allocated by the work process)
  This area is held exclusively in the memory and has nothing to do with
  the parameter rdisp/ROLL_MAXFS.
  Unit: bytes
  Default: 5000000
  When large volumes are involved, a higher value (up to 7000000) may be required in individual applications (SD, MM). In such cases, you must also increase parameter ztta/short_area (memory for intermediate results, e.g. 500000).

• rdisp/ROLL_MAXFS: maximum size of the roll file (one file per instance /usr/sap///data/ROLLFLnn)
  Unit: blocks of 8192 bytes each
  Typical value: 8192; 50 users or more per server: 16384
  Theoretical maximum value: Number of active users mutliplied by ztta/roll_area divided by 8129 (block size). This is a theoretical value (all users execute an action at the same time which use the work process-specific roll area to the maximum) which in practice will never be reached.

• rdisp/ROLL_SHM: Roll area held in shared memory
  Unit: blocks of 8192 bytes each
  In some operating systems, or when only a small amount of main memory is available, this value must be 0.
  

The size of the roll file on disk and in shared memory is displayed in transaction ST02.

Remarks concerning the new memory management (as of Rel. 3.0)

With the new memory management a dialog workprocess satisfies its need for memory consecutively from the following ressources:

• initial roll area: rolling like in releases prior to 3.0 (system parameter: ztta/roll_first, up to 3.0B: ztta/roll_area)

• extended memory: Shared memory (system parameter: ztta/roll_extension)

• as of rel. 3.0C: second part of roll area (system parameter ztta/roll_area defines the sum of both roll areas)

• "heap": memory allocated by individual process, process in private mode (system parameters: abap/heap_area_dia)
  

For a batch or an update work process the following ressources are consecutively used:

• roll area: (system parameter: ztta/roll_area)

• heap: (System parameter: abap/heap_area_nondia)

• as of rel. 3.0C: extended memory (system parameter: ztta/roll_extension)
  

For detailed documentation see Notes 31395, 33395 and 33576

Key word: Roll area