PHYS_MEMSIZE SAP Parameter attribute - Available main memory for SAP instance

PHYS_MEMSIZE is a SAP Parameter attribute which is used to control Available main memory for SAP instance information. This is available within R/3 SAP systems depending on the version and release level.

Below is the standard documentation available and a few details of the attributes values .

PHYS_MEMSIZE profile paramerter attributes

Parameter Name: PHYS_MEMSIZE
Description: Available main memory for SAP instance
Default Value: 15869
Parameter Type ( See IF_PARAMETER_TYPES): Integer range(INT_RANGE)
Restriction Values: 16 512000
Parameter Unit: MB
Parameter Group: System
CSN Component: BC-CST-MM
System-Wide parameter: No
Dynamic Parameter: No
Vector Parameter: No
Has Sub-Parameters: No
Check Function Exists: No

Parameter documentation

Important This parameter is only valid for Microsoft Windows NT. The value defines how many megabytes of the main memory are to be used for the SAP instance. The default value for PHYS_MEMSIZE is the size of the main memory in megabytes. That is, it is automatically adjusted if the main memory configuration is changed. With this value, the default values for the following memory management parameters are automatically calculated and you therefore do not need to maintain them manually.
em/initial_size_MB = [PHYS_MEMSIZE] If necessary, the extended memory extends itself by the value [PHYS_MEMSIZE / 2]. With PHYS_MEMSIZE, the maximum number of users UC] is calculated. rdisp/ROLL_SHM = [UC] * 100 ( 100 blocks per user) rdisp/ROLL_MAXFS = [UC] * 100 ( 100 blocks per user) rdisp/PG_SHM = [UC] * 50 ( 50 blocks per user) rdisp/PG_MAXFS = 32768
Aim The new default values for memory management under Microsoft Windows NT mean that you do not need to manually maintain the profile parameters. With PHYS_MEMSIZE, all memory management is calculated and adjusted. In this case, you only need to maintain this value if the SAP instance may not use the entire working memory.
Example 1 With a central instance with 1 GB of main memory, the database uses 400 MB and the application server uses 600 MB. In this case, manually set the value for PHYS_MEMSIZE to 600 in the instance profile. (No additional adjustments required)
Example 2 There are two dialog instances (for example, a production system and a test system) on one system (1 GB). With PHYS_MEMSIZE, the main memory is now divided between the two SAP instances. For example: Production system PHYS_MEMSIZE = 700 Test system PHYS_MEMSIZE = 300
Example 3 A dialog instance on a host. That is, the SAP instance can use the entire main memory and it is therefore not necessary to manually maintain PHYS_MEMSIZE, because its default value is set to the size of the main memory.

See SAP Parameter Documentation for full SAP documentation for this profile parameter.