enq: JI - contention wait event solution

Action
Synchronizing data with remote database(NEW_XE)

SQL>
BEGIN DBMS_SNAPSHOT.REFRESH(LIST =>  'HR.SS_EMPLOYEES_NEW',METHOD => 'F' ); END;

Problem
enq: JI - contention wait event occurs

Determine the problem
SQL>
  SELECT eq_name "Enqueue",
         ev.name "Enqueue Type",
         eq.req_description "Description"
    FROM v$enqueue_statistics eq, v$event_name ev
   WHERE eq.event# = ev.event# AND ev.name = 'enq: JI - contention'
ORDER BY ev.name;

Description -> Lock held during materialized view operations (like refresh, alter) to prevent concurrent operations on the same materialized view

Solution I
Kill problematic session
SQL>
  SELECT DISTINCT
            'ALTER SYSTEM KILL SESSION '''
         || SID
         || ','
         || SERIAL#
         || ''' IMMEDIATE;'
            AS KILL_THEM_ALL
    FROM V$SESSION
   WHERE     TYPE <> 'BACKGROUND'
         AND STATUS = 'ACTIVE'
         AND EVENT = 'enq: JI - contention';

Solution II
Check database link
SQL>
SELECT * FROM V$INSTANCE@NEW_XE