What to do with archived redo-logs ?

First : I'm the system administrator and NOT the database administrator, but I'm asking myself some questions about our backup-procedureof our database.
Our database runs in ARCHIVE-LOG-MODE, so it is possible to schedule ON-LINE backups.
Our backup-script does the following things : 1) executes via SQLPLUS (as sys) an SQL-script to "ALTER TABLESPACE ... BEGIN BACKUP"
2) places all the database-files, temporary table-space, Control-file, redo-logs on DAT-tape.
3) executes via SQLPLUS (as sys) an SQL-script to "ALTER TABLESPACE ... END BACKUP"
4) Places all the archived redo-logs from the archive-directory on the DAT-tape, and afterwards erase all these redo-log-file (so there is again place enough for the next day).

We execute this backup-scirpt EACH NIGHT.

I was wondering, is it necessary to put ALL the redo-log-files on DAT-tape ?
You can separate them into two groups :
A) ARCHIVED-REDO-logs created between the END-BACKUP (yesterday-night) and the BEGIN-BACKUP (in our case this are the archived-redo-logs created due to the activity of the last working day) B) ARCHIVED-REDO-logs created while the database was in BACKUP-mode and the datafiles were copied one by one on DAT-tape.

Which ARCHIVED-REDO-logs will be necessary to RECOVER the database in case of a database-crash ?
What is normaly done with REDO-logs ?

Are there people who can share their knowledge about the 'HOT' topic ? All information is welcome,
  Chris MARREEL.

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