Hello,
To be exact the parameter PHYS_MEMSIZE should be defined in the instance profile file:
<SAP drive>:\usr\sap\<SID>\SYS\profile\<SID>_DVEBMGS00_<Hostname>
88416 - Zero administration memory management for the ABAP server
As of kernel version 7.20, you can specify PHYS_MEMSIZE relative to the size of the main memory as follows:
PHYS_MEMSIZE=20%
Regards