Blocked sessions and their blockers

1CLEAR COLUMNS2SET LINESIZE 200 PAGESIZE 100 TRIMOUT ON TAB OFF3COLUMN blocked        HEADING "BLOCKED"      FORMAT A144COLUMN username       HEADING "USER"         FORMAT A155COLUMN event          FORMAT A30 TRUNCATE6COLUMN wait_secs      HEADING "WAIT SECS"    FORMAT 999,9997COLUMN blocker        HEADING "BLOCKER"      FORMAT A148COLUMN blocker_user   HEADING "BLOCKER USER" FORMAT A159COLUMN blocker_status HEADING "STATUS"       FORMAT A810COLUMN blocker_sql_id HEADING "BLOCKER SQL"  FORMAT A1311 12SELECT s.sid || ',' || s.serial# AS blocked,13       s.username, s.event,14       s.seconds_in_wait AS wait_secs,15       b.sid || ',' || b.serial# AS blocker,16       b.username AS blocker_user,17       b.status AS blocker_status,18       NVL(b.sql_id, b.prev_sql_id) AS blocker_sql_id19FROM v$session s20JOIN v$session b ON b.sid = s.blocking_session21WHERE s.blocking_session IS NOT NULL22ORDER BY s.seconds_in_wait DESC;