How to check Data Guard apply rate in Oracle

V$RECOVERY_PROGRESS reports MRP''s apply throughput. Active Apply Rate is the instantaneous rate; Average Apply Rate is smoothed over the run. Compare against redo generation on the primary — if apply < generation, the lag grows.

SELECT TO_CHAR(start_time, 'DD-MON-RR HH24:MI:SS') AS start_time,
       item,
       ROUND(sofar / 1024, 2) AS "MB/Sec"
FROM   v$recovery_progress
WHERE  item IN ('Active Apply Rate', 'Average Apply Rate');