Archive to No Archive Mode

Steps to convert the database from Archivelog Mode to No Archive log mode.

SQL> Alter system set log_archive_start=false scope=spfile;
Database Altered

SQL> Shutdown Immediate
Database Closed
Database Dismounted
Instance Shutdown

SQL> Startup Mount;
Oracle Instance started
.....
Database Mounted

SQL> Alter Database NoArchivelog;
Database Altered

SQL> Alter database Open;
Database Altered.

SQL> Archivelog list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 3108
Next log sequence to archive 3109
Current log sequence 3109

Your database is in NoArchivelog Mode.