LFAREA = {xM | xG | xT | x%}
{(xM | xG | xT | x% [,INCLUDE1MAFC])}
{( [1M=(a [,b]) | 1M=(a% [,b%])]
[,2G=(a [,b]) | ,2G=(a% [,b%])]
[,prompt | ,noprompt]
[,INCLUDE1MAFC]
)} The LFAREA parameter specifies the amount of online real storage available at IPL to reserve for backing 1 MB pages and 2 GB pages. The xM, xG, xT, and x% syntax form reserves 1 MB pages, and the 1M= and 2G= syntax form reserves 1 MB and 2 GB pages. The two syntax forms cannot be combined. Each syntax specification uses a different formula for calculating percentage requests and the system limit, as described in Request handling for the large frame area system limit and Request handling for insufficiently contiguous online real storage.
In the following descriptions, 2 GB is equal to a decimal value of 231, or 2147483648, and 4 GB is equal to a decimal value of 232, or 4294967296.
Value range: The following value ranges
apply to the value specified on the LFAREA parameter. The maximum
values that can be specified for the LFAREA are described in Request handling for the large frame area system limit.
- xM or xG or xT
- Specifies the amount of online real storage to reserve for 1 MB pages. Up to six decimal digits can be specified for x: xM specifies the amount is in megabytes; xG specifies the amount is in gigabytes; xT specifies the amount in terabytes. A specification of 0M, 0G, or 0T results in zero 1 MB pages being reserved.
- x%
- Specifies the amount of online real storage to reserve for 1 MB pages, as a percentage of the total online real storage at IPL. Up to two digits can be specified. The percentage is calculated as (x% * online real storage at IPL) – 2G. The maximum percentage that can be specified is 80%. A specification of 0% results in zero 1 MB pages being reserved.
- 1M=(a)
- Specifies the number of 1 MB pages of online real storage to reserve in the large frame area. Up to eight decimal digits can be specified for a. A specification of 1M=(0) results in zero 1 MB pages being reserved.
- 1M=(a,b)
- Specifies the number of 1 MB pages of online real storage to reserve in the large frame area. Up to eight decimal digits each can be specified for a and b. The value that is specified for a is the target number of pages, and the value that is specified for b is the minimum number. The system attempts to meet the request at or as near as possible up to the target number, but at no less than the minimum number. The value that is specified for b must be less than or equal to the value specified for a, and can be zero. A specification of 1M=(0,0) results in zero 1 MB pages being reserved. Once the LFAREA parameter has been processed, no additional amounts of storage are reserved later in an attempt to reach the target. Both a value and a percentage, such as 1M=(a,b%) or 1M=(a%,b), cannot be specified.
- 1M=(a%)
- Specifies the amount of online real storage to reserve in the large frame area for 1 MB pages, as a percentage. Up to two digits can be specified. The storage amount is calculated as a% * (online real storage at IPL – 4G), rounded down to the nearest 1 MB boundary. The maximum percentage that can be specified is 80%. A specification of 1M=(0%) results in zero 1 MB pages being reserved.
- 1M=(a%,b%)
- Specifies the amount of online real storage to reserve in the large frame area for 1 MB pages, as a percentage. Up to two digits each can be specified for a% and b%. The value specified for a% is the target amount, and the value specified for b% is the minimum amount. The system attempts to satisfy the request at or as near as possible up to the target amount, but at no less than the minimum amount. The percentages are calculated as percent * (online real storage at IPL – 4G), rounded down to the nearest 1 MB boundary. The maximum percentage that can be specified for a% is 80%. The value specified for b% must be less than or equal to the value for a%, and can be zero. A specification of 1M=(0%,0%) results in zero 1 MB pages being reserved. Once the LFAREA parameter has been processed, no additional amounts of storage are reserved later in an attempt to reach the target. Both a value and a percentage, such as 1M=(a,b%) or 1M=(a%,b), cannot be specified.
- 2G=(a)
- Specifies the number of 2 GB pages of online real storage to reserve in the large frame area. Up to eight decimal digits can be specified for a. A specification of 2G=(0) results in zero 2 GB pages being reserved. Each 2 GB page is placed only in a 2 GB area of contiguous real storage on a 2 GB boundary, which means that enough 2 GB areas of contiguous online storage on 2 GB boundaries must be available at IPL for the number of 2 GB pages requested.
- 2G=(a,b)
- Specifies the number of 2 GB pages of online real storage to reserve in the large frame area. Up to eight decimal digits each can be specified for a and b. The value specified for a is the target number of pages, and the value specified for b is the minimum number. The system attempts to satisfy the request at or as near as possible up to the target number, but at no less than the minimum number. The value specified for b must be less than or equal to the value for a, and can be zero. A specification of 2G=(0,0) results in zero 2 GB pages being reserved. Once the LFAREA parameter has been processed, no additional amounts of storage are reserved later in an attempt to reach the target. Both a value and a percentage, such as 2G=(a,a%) or 2G=(a%,a) cannot be specified. Each 2 GB page is placed only in a 2 GB area of contiguous real storage on a 2 GB boundary, which means that enough 2 GB areas of contiguous online storage on 2 GB boundaries must be available at IPL for at least the minimum number of 2 GB pages requested.
- 2G=(a%)
- Specifies the amount of online real storage to reserve in the large frame area for 2 GB pages, as a percentage. Up to two digits can be specified for a. The storage amount is calculated as a% * (online real storage at IPL – 4G), rounded down to the nearest 2 GB boundary. The maximum percentage that can be specified is 80%. A specification of 2G=(0%) results in zero 2 GB pages being reserved. Each 2 GB page is placed only in a 2 GB area of contiguous real storage on a 2 GB boundary, which means that enough 2 GB areas of contiguous online storage on 2 GB boundaries must be available at IPL for the amount of 2 GB pages requested.
- 2G=(a%,b%)
- Specifies the amount of online real storage to reserve in the large frame area for 2 GB pages as a percentage. Up to two digits each can be specified for a% and b%. The value specified for a% is the target amount, and the value specified for b% is the minimum. The system attempts to satisfy the request at or as near as possible up to the target amount, but at no less than the minimum amount. The percentages are calculated as percent * (online real storage at IPL – 4G), rounded down to the nearest 2 GB boundary. The maximum percentage that can be specified for a% is 80%. The value specified for b% must be less than or equal to the value for a%, and can be zero. A specification of 2G=(0%,0%) results in zero 2 GB pages being reserved. Once the LFAREA parameter has been processed, no additional amounts of storage is reserved later in an attempt to reach the target. Both a value and a percentage, such as 2G=(a,b%) or 2G=(a%,b), cannot be specified. Each 2 GB page is placed only in a 2 GB area of contiguous real storage on a 2 GB boundary, which means that enough 2 GB areas of contiguous online storage on 2 GB boundaries must be available at IPL for at least the minimum amount of 2 GB pages requested.
- prompt | noprompt
- Specifies whether the system prompts for re-specification of the LFAREA parameter when the request cannot be satisfied. The default is prompt, which specifies for the system to prompt when either the 1M= or 2G= request cannot be satisfied. The value noprompt specifies for the system to ignore the LFAREA request when either or both of the 1M= and 2G= requests cannot be satisfied, and to instead reserve zero 1 MB pages and zero 2 GB pages in the large frame area.
INCLUDE1MAFC
- Specifies that 1 MB pages are to be included in the available
frame count (RCEAFC).With APAR OA41968 installed, specifying INCLUDE1MAFC results in the following system behavior:
- RSM performs less paging when there is an abundance of available fixed 1 M pages in the system.
- RSM is more likely to break up fixed 1 M pages to satisfy 4 K page demand. Although RSM attempts to coalesce broken up fixed 1 M pages when there is fixed 1 M page demand, there is no guarantee that coalescing will be successful, especially if one of the 4 K frames making up the fixed 1 M page is fixed long term.
Application programs can check the RCEINCLUDE1MAFC bit to determine if the installation specified INCLUDE1MAFC in their LFAREA specification.
For RMF users, the PTF for RMF APAR OA42510 must be applied prior to specifying INCLUDE1MAFC. RMF uses the RCEAFC to generate some of their reports. Not applying OA42510 might lead to incorrect RMF reports.
In addition, application programs that use the STGTEST SYSEVENT need to be assessed to determine if any changes need to be made. STGTEST returns information about the amount of storage available in the system. If INCLUDE1MAFC is specified, available fixed 1 M pages are included in this amount.
Examples: