Turn of read-only mode after an interrupted backup

Per default a site is set in read-only mode during backup. If the backup is interrupted, e.g. if the server is rebooted after updates, the site will stay in read-only mode.

To unlock the site use the following command:

Set-SPSite -Identity http://mysite -LockState “Unlock”

Other possible states are: NoAdditions, ReadOnly, NoAccess.