Enable Readonly Mode in SharePoint 2013

To put a lock on a site collection in SharePoint 2013, and keep the site collection in the read only mode, issue the following PowerShell command.

 

Lock

 

Set-SPSite -Identity http://mysite/sites -LockState "Readonly"

 

To Unlock

 

Set-SPSite -Identity http://mysite/sites -LockState "Unlock"