LFAREA syntax and examples

Specifying the LFAREA parameter is done using one of the two separate and distinct syntax methods and percentage calculation formulas, which are shown in Table 1. Following Table 1, the subsequent tables show examples of specific LFAREA calculations and specifications.

Attention: All LFAREA calculation and specification examples are examples only, and are never to be used as a substitute for the specific calculations and specifications that are required for your z/OS® system.

Table 1 describes the two LFAREA syntax methods, and the formulas for the percentage specification.

Note: The LFAREA parameter is also described in z/OS MVS Initialization and Tuning Reference.

Table 1. The two supported LFAREA syntax methods
Syntax	Percentage formula (optional)	Usage notes
LFAREA=xM\|xG\|xT\|x%	If a percentage (x%) is specified, the system calculates the requested number of 1 MB pages to reserve using the following formula: `Number of 1 MB pages to reserve = (x% * online real storage at IPL in megabytes) - 2048 MB` or `Number of 1 MB pages to reserve = [(x% * online real storage in gigabytes) - 2 GB] * 1024` Note that the resulting 1 MB number of pages is rounded down to the next whole number of 1 MB pages (which will be zero for values less than 1 MB).	Consider the following usage notes before using this syntax method: The variable x specifies the LFAREA size in megabytes (M), gigabytes (G), or terabytes (T), or as a percentage (%). This syntax method reserves only the 1 MB large frame area. To define the 2 GB large frame area, you must use the alternative syntax method which specifies 1M= and 2G= values. This syntax method provides compatibility with your prior z/OS version when a percentage is specified because it uses the same formula and reserves the same number of 1 MB pages that were reserved on your prior z/OS version.
LFAREA=(1M=(target[%],minimum[%]), 2G=(target[%],minimum[%]))	If percentages (target% and minimum% ) are specified, the requested target and minimum number of 1 MB pages to reserve are calculated using the formula: `number of 1 MB pages to reserve = (target% or minimum%) * (online real storage at IPL in megabytes - 4096 MB)` or `number of 1 MB pages to reserve = (target% or minimum% * (online real storage at IPL in gigabytes - 4 GB)) * 1024` If percentages (target% and minimum%) are specified, the requested target or minimum number of 2 GB pages to reserve is calculated using the formula: `number of 2 GB pages to reserve = target% or minimum% * (online real storage at IPL in 2 gigabytes - 4 GB)` Note that the resulting 1 MB or 2 GB number of pages is rounded down to the next respective 1 MB or 2 GB whole number of pages (which will be zero for values less than 1 MB or 2 GB).	Consider the following usage notes before using this syntax method: The target and minimum values specify either the number of pages or the percentage of online real storage at IPL as calculated using the percentage formula. This syntax method can reserve both 1 MB and 2 GB large frame areas. You cannot combine both fixed and percentage target and minimum values within each 1 MB or 2 GB specification.