Helps when doing Management Pack Tuning for SCOM

MPTuining-RulesAndUnitMonitors.ps1

param(
    [Parameter(Mandatory=$true)]
    [string]$sourceManagementPackDisplayName,

    [Parameter(Mandatory=$true)]
    [string]$overrideManagementPackDisplayName,

    [Parameter(Mandatory=$true)]
    [ValidateSet('unitMoninitor','rule')]
    [string]$itemType,

    [Parameter(Mandatory=$true)]
    [ValidateSet('True','False')]
    [string]$itemsToBeEnabled,

    [Parameter(Mandatory=$true)]
    [ValidateScript({Test-Path -path $_ })]
    [string]$inputFilePath
)

Import-Module OperationsManager

$comment    = "Overriden by: $($env:USERNAME); On: $(Get-Date) "
$sourceMP   = Get-SCOMManagementPack -DisplayName $sourceManagementPackDisplayName
$overrideMP = Get-SCOMManagementPack -DisplayName $overrideManagementPackDisplayName

if ($itemType -eq 'rule') {

    $rules         = $sourceMP | Get-SCOMRule
    $rulesFromFile = Get-Content -Path $inputFilePath

    $rules | ForEach-Object {
        $rule = $_
        $rulesFromFile | ForEach-Object {
            if ($rule.DisplayName -match $_) {
                $targetClass          = Get-ScomClass -Id $rule.Target.Id
                $overrideName         = $rule.Name + ".Override"
                $override             = New-Object Microsoft.EnterpriseManagement.Configuration.ManagementPackRulePropertyOverride($overrideMP,$overrideName)
                $override.Rule        = $rule
                $override.Property    = 'Enabled'
                $override.Value       = $itemsToBeEnabled
                $override.Context     = $targetClass
                $override.Description = $comment
                $override.DisplayName = $overrideName
            }
        }
    }

} else {

    $monitors         = $sourceMP | Get-SCOMMonitor | Where-Object {$_.xmltag -eq "UnitMonitor"}
    $monitorsFromFile = Get-Content -Path $inputFilePath

    $monitors | ForEach-Object {
        $monitor = $_
        $monitorsFromFile | ForEach-Object {
            if ($monitor.DisplayName -match $_) {
                $targetClass          = Get-ScomClass -Id $monitor.Target.Id
                $overrideName         = $monitor.Name+".Override"
                $override             = New-Object Microsoft.EnterpriseManagement.Configuration.ManagementPackMonitorPropertyOverride($overrideMP,$overrideName)
                $override.Monitor     = $monitor
                $override.Property    = 'Enabled'
                $override.Value       = $itemsToBeEnabled
                $override.Context     = $targetClass
                $override.Description = $comment
                $override.DisplayName = $overrideName
            }
        }
    }

} #end if ($itemType -eq 'rule')

$overrideMP.Verify()
$overrideMP.AcceptChanges()

Inspired by other sources, e.g.:
https://social.technet.microsoft.com/wiki/contents/articles/30714.scom-2012-bulk-override-creation-for-monitors-and-rules-using-powershell.aspx