SAP Note 23863 - MEMORY MANAGEMENT 3.0

Symptom:

Storage problems.

Cause and prerequisites

Insufficient profile settings.

Solution
In Release 3.0 there are 3 storage areas which must be set by profile parameters so that the respective applications run with optimal performance. In addition to the classical roll area, 3.0 also contains the EM storage area (Extended memory area), which accesses the 'shared memory' resources, as well as the 'heap' memory which uses operating system storage areas (malloc).

Relevant parameters:

ROLL:
ztta/roll_area Size of the entire roll / internal mode
ztta/roll_first Size of the 1st roll area segment
(from 3.0C)
rdisp/ROLL_SHM Roll buffer in 8KB blocks

EM:
ztta/roll_extension Quota of one user in EM (bytes)
em/blocksize_KB EM Block size in KB, 1024 to n
em/initial_size_MB Created on the install date
em/max_size_MB ... NN
em/address_space_MB Reserved address space (only NT)

HEAP:
abap/heaplimit Limit in the heap (bytes), beyond which the WP is restarted.
Storage is then available again
for other processes.
abap/heap_area_dia Heap / user online
abap/heap_area_nondia Heap / user in background processes + update
abap/heap_area_total Sum of all heap storage / Application servers
Restrictions and special features of the storage classes:
The EM resource in shared memory is limited to approx. 1 GB per UNIX machine. The total of all processes must not exceed this quantity. In contrast to the heap, however, a user with a WP in EM can move to another one. This is not possible for the process-specific heap memory.

This is a temporary recommendation with the request to update the information here:
Smaller transactions should take their storage requirement purely from the ROLL. It is therefore recommended that you use a roll of 1 MB (standard). The entire roll area can be set to 16MB - it is only required if the EM area is used up.
The EM area replaces the old SAP paging. The larger EM/initial_size_MB is, the more SWAP must be configured on a machine. 1 GB of memory is ideal.
HEAP:
Background, update and spool processes take their memory from the ROLL and HEAP. Only if these areas are exhausted, is the remaining EM used.
Important for the installation: The operating system must generally be recompiled so that sbrk (malloc) is not limited to a few MB per process. As the amount of storage required for background processing can be very considerable, the value must be set correspondingly. The swap space on the machines should be increased.

Note: The 3.0 MM is released with 3.0A.
With the report RSMEMORY, the apportionment of individual areas can be checked in the current system. Display according to users is available under the menu option Goto ..
Moreover, you can use System -> Utilities -> Resource usage to check the storage usage of individual transactions.
From Release 3.0C, you can use transactions RZ03 and ST02 to display the occupancy level of the storage types. This display forms the basis of tuning measures.
RZ03 -> Additional views > Storage management: Shows the current usage of all R/3 instances.
ST02 shows the current usage and history of an R/3 instance.