Below is a basic script to lockout Content Database for new site collections. It sets the max to current sites count and warning to less than 1 of count. May help someone.
$ALLDB = Get-SPContentDatabase
foreach($DB in $ALLDB)
$Count = $DB.Sites.Count
if($Count -gt 0)
$CountWarnining = $Count – 1
Set-SPContentDatabase $DB.Name -MaxSiteCount $Count -WarningSiteCount $CountWarnining
Get-SPContentDatabase | Select Name, Current*, Max*, WarningSiteCount | Out-GridView