PowerShell Function to Set Page File Initial/Maximum Size

The PowerShell 2.0 function below, Set-PageFile, sets a page file to the given initial and maximum size.

At first sight this seems to be an easy task – just set the properties InitialSize and MaximumSize accordingly (Win32_PageFileSetting class). The tricky part is that the system won’t let you change any page file setting as long as the system automatically manages these settings. My function takes care of this fact and disables the Win32_ComputerSystem‘s AutomaticManagedPagefile property if necessary.

The function supports PowerShell’s -WhatIf switch. Therefore you can test it safely without any impact.

function Set-PageFile
{
    <#
    .SYNOPSIS
        Sets Page File to custom size

    .DESCRIPTION
        Applies the given values for initial and maximum page file size.

    .PARAMETER Path
        The page file's fully qualified file name (such as C:\pagefile.sys)

    .PARAMETER InitialSize
        The page file's initial size [MB]

    .PARAMETER MaximumSize
        The page file's maximum size [MB]

    .EXAMPLE
        C:\PS> Set-PageFile "C:\pagefile.sys" 4096 6144
    #>

    [CmdletBinding(SupportsShouldProcess=$True)]
    param (
        [Parameter(Mandatory=$true,Position=0)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Path,
        [Parameter(Mandatory=$true,Position=1)]
        [ValidateNotNullOrEmpty()]
        [Int]
        $InitialSize,
        [Parameter(Mandatory=$true,Position=2)]
        [ValidateNotNullOrEmpty()]
        [Int]
        $MaximumSize
    )
    
    Set-PSDebug -Strict

    $ComputerSystem = $null
    $CurrentPageFile = $null
    $Modified = $false

    # Disables automatically managed page file setting first
    $ComputerSystem = Get-WmiObject -Class Win32_ComputerSystem -EnableAllPrivileges
    if ($ComputerSystem.AutomaticManagedPagefile)
    {
        $ComputerSystem.AutomaticManagedPagefile = $false
        if ($PSCmdlet.ShouldProcess("$($ComputerSystem.Path.Server)", "Disable automatic managed page file"))
        {
            $ComputerSystem.Put()
        }
    }

    $CurrentPageFile = Get-WmiObject -Class Win32_PageFileSetting
    if ($CurrentPageFile.Name -eq $Path)
    {
        # Keeps the existing page file
        if ($CurrentPageFile.InitialSize -ne $InitialSize)
        {
            $CurrentPageFile.InitialSize = $InitialSize
            $Modified = $true
        }
        if ($CurrentPageFile.MaximumSize -ne $MaximumSize)
        {
            $CurrentPageFile.MaximumSize = $MaximumSize
            $Modified = $true
        }
        if ($Modified)
        {
            if ($PSCmdlet.ShouldProcess("Page file $Path", "Set initial size to $InitialSize and maximum size to $MaximumSize"))
            {
                $CurrentPageFile.Put()
            }
        }
    }
    else
    {
        # Creates a new page file
        if ($PSCmdlet.ShouldProcess("Page file $($CurrentPageFile.Name)", "Delete old page file"))
        {
            $CurrentPageFile.Delete()
        }
        if ($PSCmdlet.ShouldProcess("Page file $Path", "Set initial size to $InitialSize and maximum size to $MaximumSize"))
        {
            Set-WmiInstance -Class Win32_PageFileSetting -Arguments @{Name=$Path; InitialSize = $InitialSize; MaximumSize = $MaximumSize}
        }
    }
}