Log management

Switch to archivelog mode :

alter system set log_archive_dest_1='LOCATION=/oracat/log/ORACAT/archive' scope=both;

shutdown immediate;
startup mount;

alter database archivelog;

alter database open;

alter system switch logfile;
archive log list;

Check the recovery area :

show parameter recovery

Change between archivelog / noarchivelog mode

shutdown immediate;
startup mount;
alter database archivelog / noarchivelog;
alter database open;