Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _WINSTA_H

typedef enum _LOADFACTORTYPE
    ErrorConstraint, // An error occurred while obtaining constraint data.
    PagedPoolConstraint, // The amount of paged pool is the constraint.
    NonPagedPoolConstraint, // The amount of non-paged pool is the constraint.
    AvailablePagesConstraint, // The amount of available pages is the constraint.
    SystemPtesConstraint, // The number of system page table entries (PTEs) is the constraint.
    CPUConstraint // CPU usage is the constraint.


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This type is documented in the [MS-TSTS] specification.