set Lock State (No Access, ready only, no additions, unlock) of all site collections in a SharePoint farm using powershell

Normally site lock functionality is available at site collection level only and not at farm level or even web application level, I came across a requirement where in I was asked to lock all site collections in farm. Since my farm has more than 20000 site collection it would have been a tedious task if I had to to it manually one by one.

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Have created a Powershell script to set the all site collection in a farm to "NO Access" mode.

Add-PSSnapin Microsoft.SharePoint.PowerShell -erroraction SilentlyContinue;

Start-SPAssignment -Global;

$webapps= Get-SPWebApplication;

$LockState= "NoAccess"; 

Write-Host "Setting all web applications to $($LockState)..." -ForegroundColor Yellow;

foreach ($webapp in $webapps)

{

$sites= Get-SPSite -WebApplication $webapp -Limit All;

$sites | ForEach-Object{

Write-Host "Setting site collection $_.Url to $($LockState)..." -ForegroundColor Yellow;

        Set-SPSiteAdministration -LockState $LockState -Identity $_.url;}

}

Stop-SPAssignment -Global;

Write-Host "Finished!" -ForegroundColor Green;

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Below are the valid values for LockState variable 

• Unlock to unlock the site collection and make it available to users.
• NoAdditions to prevent users from adding new content to the site collection. Updates and deletions are still allowed.
• ReadOnly to prevent users from adding, updating, or deleting content.
• NoAccess to prevent users from accessing the site collection and its content. Users who attempt to access the site receive an error message.