ztta/roll_extension: Extended Memory Limit
Use
The value specifies the amount of memory that one user context can allocate to the SAP extended memory. This value is valid for all types of work processes.
You can also control the quotas for dialog and non-dialog work processes separately. To do this use parameters ztta/roll_extension_dia and ztta/roll_extension_nondia. For example, you can give a larger proportion of extended memory to batch processes than to dialog work processes.
A very large memory area set by the parameter setting em/initialsizeMB defines the Extended Memory, where most or all of the user context of the user will reside while executing a program. After consuming the first roll area defined by ztta/roll first, a dialog work process will start allocating extended memory. SAP Extended Memory. SAP extended memory is the core of the SAP memory management system. Each SAP work process has a part reserved in its virtual address space for extended memory (see Virtual Address Space in a Work Process). You can set the size of extended memory using the profile parameter em/initialsizeMB: Extended Memory Pool Size.
Integration
The EM quotas for work processes must not be more than the total amount of extended memory.The total size of the extended memory is specified in the em/initial_size_MB parameter.
Using the CCMS alert monitor (transaction RZ20), you can determine how much extended memory your servers use. The peak value displays the “high water mark” (maximum allocation) for extended memory.
Features
The parameter determines how much SAP Extended Memory a User Context can allocate.
The graphic below shows this relationship:
If the value is exceeded, heap memory is allocated. The work process is assigned only to this user context and is no longer available for other user contexts, since it is switched to the PRIV mode (in the Work Process Monitor, transaction SM50). See: Private Memory
If the value is set too high, caused by a large user context, an extended memory bottleneck can occur. If a large user context fills the SAP extended memory, it can switch other smaller work processes used for user contexts into PRIV mode before their SAP extended memory limit has been used up.
Activities
Sap Extended Memory Parameter Examples
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.
If you have problems with the default value, SAP recommends that you test your system with a high value (at least 500 MB). If the PRIV mode is switched on prematurely, you can decrease the size.
To minimize the number of dialog work processes in the PRIV mode, keep in mind the following tips:
Sap Extended Memory Parameter Example
·em/initial_size_MB: should be significantly larger than ztta/roll_extension.
Sap Parameter Id
·rdisp/ROLL_SHM, rdisp/ROLL_MAXFS: If you increase the value of ztta/roll_area, you must adjust these parameters.