slowness in query execution

Note; I have tried running each Update query from  the block below separately but still never get it to complete for days

Declare

Begin

UPDATE user_metadata u

      SET u.metadata =CASE

                              WHEN EXISTSNODE(u.metadata, '/hash/src/text()') = 0

                                THEN insertChildXML(u.metadata, '/hash', 'src', XMLTYPE('<src>S001</src>'))

                               ELSE u.metadata

                              END

where CLIENT_ID = 10021;

UPDATE user_metadata u

      SET u.metadata = CASE

                              WHEN EXISTSNODE(u.metadata, '/hash/practices') = 0

                                THEN insertChildXML(u.metadata, '/hash', 'practices', XMLTYPE('<practices nil="true"></practices>'))

                               ELSE u.metadata

                              END                                                            

where CLIENT_ID = 10021;

UPDATE user_metadata u