SQL> archive log list
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 84
Current log sequence 86
SQL> shutdown immediate
Database closed.
Database dismounted.
Oracle instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 608174080 bytes
Fixed Size 780320 bytes
Variable Size 170924000 bytes
Database Buffers 436207616 bytes
Redo Buffers 262144 bytes
Database mounted.
SQL> alter database archivelog;
Database altered.
SQL> alter database open
Database altered.
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 84
Next log sequence to archive 86
Current log sequence 86