query to see if you are in ARCHIVELOG mode:
This can also be queried in Oracel SQL developer.

SQL> archive log list;
SQL> select log_mode from v$database;
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You can also run this UNIX/Linux command 
to see if you are running in archivelog mode.  
If you are in ARCHIVELOG mode, 
you will see rows returned by this ps command:

$ ps -ef|grep -i _arc