SharePoint portalsuperreaderaccount and portalsuperuseraccount

Get and Set super reader and super user accounts

How to get and set the SharePoint portalsuperreaderaccount and portalsuperuseraccount:

$w = Get-SPWebApplication "url"
$w.properties["portalsuperuseraccount"] = "domain\username"
$w.properties["portalsuperreaderaccount"] = "domain\username"
$w.Update()
Write-Host "superreader: " $w.properties["portalsuperreaderaccount"]
Write-Host "superuser: " $w.properties["portalsuperuseraccount"]

Error message that can appear if not properly set:

Object Cache: The super reader account utilized by the cache does not have sufficient permissions to SharePoint databases.
To configure the account use the following command 'stsadm -o setproperty -propertyname portalsuperreaderaccount -propertyvalue account -url webappurl'. It should be configured to be an account that has Read access to the SharePoint databases.
 Additional Data:
 Current default super reader account: NT AUTHORITY\LOCAL SERVICE

Or this error message

Trying to store a checked out item (/PAGES/PAGENAME.ASPX) in the object cache.  This may be because the checked out user is accessing the page, or it could be that the SharePoint system account has the item checked out.  To improve performance, you should set the portalsuperuseraccount property on the web application.  See the documentation for more information.