Memory allocation sequence to non dialog work processes in SAP

This article answers the following queries:

• What is the memory allocation sequence to non dialog work processes (background, update, enqueue and spool workprocesses in SAP?
• What are the SAP parameters used to define initial roll area, extended memory, heap memory, roll area ?
• What is the memory allocation sequence to non dialog work processes in Windows NT?

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Memory allocation sequence to dialog workprocesses is same in SAP for all the platforms.

However memory allocation sequence to non-dialog workprocesses is bit different based on Platform. In Windows NT, memory allocation sequence for non-dialog workprocesses is same as that of dialog workprocess memory allocation sequence in other platforms.

Memory allocation sequence to non dialog work processes in SAP as below (except in windows  NT) :

1. Initially memory is assigned from the Roll memory. Roll memory is defined by SAP parameter  ztta/roll_area and it is assigned until it is completely used up.

If the roll  memory  is full  then

2. Heap memory is allocated to the non-dialog workprocess.  Heap memory is available until one of the following occurs :

• Either the limit of the heap memory for non-dialog workprocesses is reached (defined by the SAP parameter abap/heap_area_nondia) or the entire heap memory  of all workprocesses of an SAP application server reaches its limit which is defined by parameter abap/heap_area_total
• Operating system limits of allocating memory
• The swap space in the host system is completely used up. However this situation should not occur often which results in severe performance issues.Please check swap space requirements for various platforms and define swap space optimally to avoid this issue.
• If all the above mentioned heap memory is completely used up then a non-dialog workprocess can use the SAP extended memory defined by SAP parameter em/initial_size_MB.

Related Links : 

 Memory allocation sequence to a dialog work process in SAP