The configuration of the resources managed by the memory management function (virtual address space, main memory and expanded storage) can be defined at system initialization by means of entries in the parameter file.
The SYSSIZE parameter is not required anymore. See the note on "Notes on the SYSSIZE parameter (size of the system address space on SUs /390)" for more information.
The keyword for the BEGIN record of the parameter service is MEMORY.
The maximum number of permissible parameter records is 16.
Format of the parameter record for memory management
SHRSIZE n | |
ASAMCTRL n | |
ALAMCTRL n | |
MEM-TEST n | Ignored on SUs x86 |
SHXSIZE n | Ignored on SUs /390 |
BIG-PAGE-QUOTA n | Ignored on SUs /390 |
BIG-PAGE-SHRSIZE n | Ignored on SUs /390 |
PAGING-SATURATION-WARNING-LIMIT n [,UNIT=4KB / MB ] | |
PAGING-SATURATION-LIMITS-QUOTA n |
SHRSIZE n
Size of class 4 memory below the 16 MB boundary reserved for virtual address space. This address space is needed for shared code, DSSM subsystems and TU logicals.
n is the size of the reserved space in MB.
The memory areas reserved using SHRSIZE may not exceed 8 MB.
Possible values: 1 <= n <= 8
Default value: n = 2
ASAMCTRL n
This parameter is used to set the Test and Trace Facility (TTF) built into ASAM. It specifies the size of the class 3 memory to be allocated for trace output, in 4Kbyte blocks. The TTF is intended only for error diagnosis and should be activated only if needed.
n is the size of the TTF area in 4Kbyte blocks.
Permissible values: 0 £ n £ 15
Default value: 0
ALAMCTRL n
This parameter serves to set the Test and Trace Facility (TTF) which is built into ALAM. It specifies the size of the class 3 memory to be allocated for trace output, in 4Kbyte blocks. The TTF is intended only for error diagnosis and should be activated only if needed.
n is the size of the TTF area in 4Kbyte blocks.
Permissible values: 0 <= n <= 15
Default value: 0
MEM-TEST n
This parameter specifies if and when a main memory test should be performed.
n designates the option for the main memory test. Possible values for n:
0 | No memory test on system start or during system operation. |
1 | The memory test should be performed on system start. In the case of large main memories, this may slow down system start. |
2 | Before any main memory page is allocated to a virtual page, the main memory page should be tested. This option may have a negative effect on system performance. |
Default value: n = 0
The parameter is ignored on SUs x86.
SHXSIZE n
Size of the class 4 memory created in the area above the 16 MB boundary and below the 2 GB boundary. BLS and DSSM use this address space to load shared programs and non-privileged subsystems which are present in x86-64 code. The area is embedded in all the address spaces and can be read, but not written, in non-privileged mode.
n is the size of the area in MB and must be a multiple of 16.
Possible values for n: 16, 32, 48, ...,128
Default value: n = 64
If other values are entered, system initialization is aborted.
The parameter is ignored on SUs /390.
BIG-PAGE-QUOTA n
This parameter is used to define the target size for the proportion of main memory which is to be reserved for “big pages”. A big page is 4 MB in size and is used for CISCFW compiled code.
n is the size of main memory envisaged for big pages in %.
Possible values: 1 <= n <= 99
Default value: n = 40
The parameter is ignored on SUs /390.
BIG-PAGE-SHRSIZE n
This parameter is used to define the size of the “shared big pages” which are created in the shared memory (class 3) and are used for CISCFW compiled code of shared programs.
n is the size of the shared big pages in MB and must be a multiple of 16.
Possible values: 0 <= n
Default value: n = 64
The parameter is ignored on SUs /390.
PAGING-SATURATION-WARNING-LIMIT n [,UNIT=4KB / MB ]
This parameter defines a threshold value for the number of unreserved pages in the paging memory. If the value is below the threshold, the following warning messages are issued:
EXC0873 NEW PAGING MEMORY SATURATION LEVEL = 1
EXC0873 NEW PAGING MEMORY SATURATION LEVEL = 0
These messages warn of a saturation state level 2 (threshold value 256), which would be reached otherwise.
You can find further information on the saturation states in the section "Paging memory".
n is the number of unreserved pages in the paging memory.
Possible values: 256 <= n <= 4,194,304 if UNIT=4KB
Possible values: 1 <= n <= 16,384 if UNIT=MB
Default value: n = 256, UNIT = 4KB
PAGING-SATURATION-LIMITS-QUOTA n
With this parameter, a percentage of 100 or higher can be specified. The threshold values for the saturation states level 2 and 3 in the paging memory (in case of memory saturation) and for the saturation states level 1 and 0 (in case of desaturation) are multiplied with this percentage. This ensures that the saturation states level 2 and 3 are reported earlier than with the default settings. Accordingly, the saturation states level 1 and 0 are reported later.All threshold values refer to the number of unreserved pages in the paging memory.
You can find further information on the saturation states in the section "Paging memory".
n is the percentage of the multiplication of the threshold values.
Possible values: 100 <= n <= 1,638,500 (in percent)
Default value: n = 100
Notes on the SYSSIZE parameter (size of the system address space on SUs /390)
This parameter is not needed anymore since the area available for the system address space is calculated from the size of the user address space and the size of the entire address space resulting from this.
However, if a value is specified for SYSSIZE in the MEMORY parameter set in spite of this, then it is compared to the value calculated for SYSSIZE as a consistency check.
Possible values: 240, 256, ..., 512 MB (multiples of 16).
If any other value is entered, the system initialization is aborted.
If a value is specified for SYSSIZE and it is less than the calculated value, then the specified value is ignored and the calculated value is used.
If a value is specified for SYSSIZE and the value for the size of the entire address space resulting from the specified value is greater than 2 GB, then the system initialization is aborted with an appropriate message.
If a value is specified for SYSSIZE and results in the doubling of the size of the entire address space, then the system initialization is continued with the higher value for the entire address space. An appropriate message is output that points out the inconsistency between the generated value and the value in the parameter file.