ORA Database Error Messages ORA-16726: the external condition supplied to resource guard is invalid October 6, 2015 mpbod ORA-16726: the external condition supplied to resource guard is invalid Cause: Internal error Action: Contact Oracle Support Services. Back to previous menu Share this:Click to email a link to a friend (Opens in new window)Click to print (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Tumblr (Opens in new window)Click to share on Twitter (Opens in new window)Click to share on Pinterest (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on Pocket (Opens in new window)