SQL> alter system set log_archive_dest_1='LOCATION=+ARCH/' scope=both sid='*';
System altered.
SQL> archive log list
Database log mode             Archive Mode
Automatic archival       Enabled
Archive destination      +ARCH
Oldest online log sequence 724
Next log sequence to archive  726
Current log sequence          726
SQL> alter system switch logfile;
System altered.
For disabling archive mode also  . steps are same