This parameter is used to control the release of SAP Extended Memory) for the operating system.
For more information see Release of SAP Memory for the Operating System.
This parameter specifies in kilobytes the size of the upper part of an EM block that is also released for the operating system. It combines the benefit of smaller EM blocks (em/blocksize_KB) with regard to the main memory requirement, with the benefit of larger EM blocks with regard to performance. The size of EM blocks is determined by the em/blocksize_KB parameter.
A value of 0 means that this parameter is inactive. This is also the default setting.