Old or New Memory Management?

This section of documentation describes the conditions under which you can use the new memory management function, and how to activate the function.

Activating the New Memory Management Function

In SAP releases lower than 6.20, activate the new memory management function by setting the profile parameter es/implementation = map. In SAP Web Application Server 6.20, the new function is activated as standard.

Note that in the new memory management function, the parameter em/initial_size_MB now only sets the initial size of the EM backing store, and not the area visible in the virtual address space. em/address_space_MB is used to specify the maximum size of the extended memory for a single user context.

SAP note 386605 describes in detail how to use the new memory management function, the prerequisites for using the new memory management function, and sample configurations.

Zero Administration Memory Management

When you activate the new memory management function, the profile parameters listed below are automatically set to meaningful default values. The profile parameter PHYS_MEMSIZE is used to specify the size of the main memory available for the SAP instance.

PHYS_MEMSIZE can be set in megabytes or as a percentage of the available main memory. You can also not set it at all. If this parameter is not set, the SAP system assumes that the whole main memory is available for the SAP instance.

You can of course change the default values by overwriting them in the profile.

  • SAP Roll Area: ztta/roll_area, ztta/roll_first
  • Extended memory (EM) quota for a user context: ztta/roll_extension
  • Roll file, paging file, and the corresponding buffers: rdisp/ROLL_MAXFS, rdisp/PG_MAXFS, rdisp/ROLL_SHM, rdisp/PG_SHM
  • EM resources: em/initial_size_MB, em/max_size_MB, em/address_space_MB, em/blocksize_KB

em/address_space_MB specifies the resources for extended memory for a user context, while ztta/roll_extension specifies the quota. This means that the lower of the two parameters limits the EM for the user context.

Note that the heap parameter abap/heaparea* is not set automatically.

Availability of the New Memory Management Function

The following table gives you an overview of the SAP releases and kernel patch levels that you need – besides the Linux kernel 2.4 – for the new memory management function.

SAP release (Basis or SAP Web AS)

Kernel patch level with which the new memory management function is available

Kernel patch level with which the new memory management function is available

4.5B

731

731

4.6D

488

1040

6.10

Use backwards-compatible 6.20 kernel

6.20

0

0 (default)

Linux Kernel Version

Which Linux kernel are you using?

See the relevant section of documentation:

Linux Kernel 2.2

Linux Kernel 2.4 and Higher