How to recover oracle database if the archive log/redo log file is missing ?

steps are below ....

1) Set _ALLOW_RESETLOGS_CORRUPTION=TRUE in init.ora file.
2) Startup Mount
3) Recover database
4) Alter database open resetlogs.
5) reset undo_management to "manual" in init.ora file.
6) startup database

after then

I) perform a full-database export,
II) create a brand new and separate database, and finally
III) import the export dump.


7) Create new undo tablespace
changed undo_management to "AUTO" and undo_tablespace to "New undo tablespace"

9) restart the database.