ORA Database Error Messages ORA-12166: TNS:Client can not connect to HO agent August 4, 2015 mpbod ORA-12166: TNS:Client can not connect to HO agent Cause: NVstring contained DESCRIPTION/HO. Action: Call HO agent from integrating server. Back to previous menu https://support.oracle.com/ http://www.oracle.com/ 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)