This value specifies the extended memory pool size that the SAP system manages for the SAP Extended Memory.
The value is stated in megabytes.
Ideally, this pool is large enough to contain the sum of all the user contexts. The pool must always be larger than the size of the parameter ztta/roll_extension. This parameter specifies how much extended memory can be allocated from the pool to one user context.
If the pool is used up, heap memory is allocated (see Private Memory and Allocating Memory for User Contexts). The work process switches to the PRIV mode and is reserved exclusively for the current user context. After processing the user context, the work process might restart automatically if the process size specified in abap/heaplimit is exceeded.
The default value is platform-specific and is determined dynamically. The default value is specified in transaction RZ11. This value should not normally be changed.
The value must be between 32 and 8096.
Kep in mind the following notes about the pool size:
Ensure that the pool is 10 to 15 times as big as ztta/roll_extension. The exact value depends on the available swap space and the number of users in the host system.
The swap space must be sized so that it can contain the SAP extended memory and has enough space for the SAP usage of heap memory (see Swap Space Requirements). There must also be enough space available for competing system users outside of the SAP system. The swap space must also be large enough to ensure a safety reserve.