How to check RMAN backup progress in Oracle

V$SESSION_LONGOPS tracks any operation Oracle expects to run longer than six seconds. Filtering OPNAME LIKE ''RMAN%'' surfaces backup pieces still running, with SOFAR / TOTALWORK converted to a percentage — so you can see whether a long backup is stuck or just slow.

SELECT sid, serial#, context, sofar, totalwork,
       ROUND(sofar / totalwork * 100, 2) AS "%_COMPLETE"
FROM   v$session_longops
WHERE  opname LIKE 'RMAN%'
AND    opname NOT LIKE '%aggregate%'
AND    totalwork != 0
AND    sofar <> totalwork
ORDER BY 6 DESC;