Check Archivelog Mode
There're two ways that can check whether archivelog mode is enabled or not.
By SQL*Plus command
To use SQL*Plus specific command, you have to login to the database first.
C:\Users\scott>sqlplus sys@orclcdb as sysdba
...
Enter password:
Use SQL*Plus command archive log list to retrieve some related information about redo and archived log.
Archivelog Mode
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 9023
Current log sequence 9025
NoArchivelog Mode
SQL> archive log list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 9023
Current log sequence 9025
By SQL Query
A simple query on the database, no matter the database is MOUNT or OPEN, can get the result like this.
Archivelog Mode
SQL> select log_mode from v$database;
LOG_MODE
------------
ARCHIVELOG
NoArchivelog Mode
SQL> select log_mode from v$database;
LOG_MODE
------------
NOARCHIVELOG
For your reference, I have talked about pros and cons of enabling and disabling archivelog mode in another post.