PAGEFRAMESIZE

Derivation: PAGE FRAME SIZE

PAGEFRAMESIZE specifies the preferred page frame size in virtual storage for HEAP, ANYHEAP, and STACK storage that is obtained during application initialization and runtime.

The default value for non-CICS applications is PAGEFRAMESIZE(4K,4K,4K).

PAGEFRAMESIZE is ignored under CICS®.

Syntax

                     .-4K--------------.      
>>-PAGeframesize--(--+-----------------+--,--------------------->
                     '-heap_frame_size-'      

   .-4K-----------------.     .-4K---------------.      
>--+--------------------+--,--+------------------+--)----------><
   '-anyheap_frame_size-'     '-stack_frame_size-'      

heap_frame_size

Specifies the preferred page frame size in virtual storage for initial heap storage allocation and any subsequent heap increments. The page frame size can be specified as one of the following values:

4K

Requests the default value of 4-KB pages.

1M

Requests that 1-MB large pages be used, if available.

anyheap_frame_size

Specifies the preferred page frame size in virtual storage for initial anywhere heap storage allocation and any subsequent anywhere heap increments. The page frame size can be specified as one of the following values:

4K

Requests the default value of 4-KB pages.

1M

Requests that 1-MB large pages be used, if available.

stack_frame_size

Specifies the preferred page frame size in virtual storage for initial stack storage allocation and any subsequent stack increments. The page frame size can be specified as one of the following values:

4K

Requests the default value of 4-KB pages.

1M

Requests that 1-MB large pages be used, if available.

Usage notes

• You cannot set PAGEFRAMESIZE at the system level or region level.
• You cannot specify PAGEFRAMESIZE with the CEEBXITA assembler user exit interface.
• In an XPLINK environment, the stack_frame_size suboption only applies to the upward-growing stack.
• If 1-MB page frames are not available, the default 4-KB page frame size will be used. No message is issued to indicate this behavior.
• Page frame sizes larger than 4 KB are not allowed below the 16-MB line. If a PAGEFRAMESIZE parameter specifies 1 MB but that storage type is allocated below the 16-MB line, then the default 4-KB page frames is used. No message is issued to indicate this behavior; however, the runtime options report will show the value that was specified.
• If any PAGEFRAMESIZE parameter specifies 1M, then all of the storage preallocated to the enclave will request 1-MB page frames. The previous two usage notes apply as well.
• By default, THREADSTACK storage comes from the library heap storage that is allocated with the ANYHEAP runtime option. To use 1-MB page frames for the THREADSTACK, ensure the anyheap_frame_size suboption specifies 1M.
• When running in a preinitialized environment with an @GETSTORE service routine, a flag is passed to indicate that storage was requested to be backed by 1-MB page frames. For more information about using 1-MB page frames with an @GETSTORE service routine, see z/OS Language Environment Programming Guide.

Performance considerations