Finding the sequence of the last full backup

You are correct that to recover to a specific point in time, you need a backup and archived redo logs up to that point in time. One of the things that many sites do is keep multiple generations of their backups, just in case the most recent backup isn't good for some reason. If you keep multiple generations of your backups, you'll need all of the archived redo logs that go with it.

You can query V$LOG_HISTORY to know the SCN numbers in a particular archived redo log, along with the time that the archived redo log holds its first SCN. A query similar to the following can help you:

SELECT
sequence#,first_change#,TO_CHAR(first_time,'MM/DD/YY
HH24:MI:SS') AS time
FROM v$log_history;

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