List the SCN values describing read and apply progress
Columns
___________________________
APPLIED_SCN
APPLIED_TIME
Estimate of the time the applied_scn was generated
READ_SCN
All log data greater than this SCN has been preserved in the database
READ_TIME
Estimate of the time the read_scn was generated
NEWEST_SCN
The most recent SCN available on standby.
NEWEST_TIME
Estimate of the time the newest_scn was generated