Please check the below link for point (8.1.1 : Deprecation of Non-CDB Architecture ). https://docs.oracle.com/database/121/UPGRD/deprecated.htm#BABDBCJI "Deprecation" means "at some stage in future, Oracle *might* stop doing enhancements on this features, and at some stage after that, Oracle *might* no longer support it". In 12.1.0.1.0 non-CDB (old architecture) is not deprecated whereas from 12.1.0.2.0 it got deprecated. Even if you have single database, it is better to have it in multitenant architecture as 1CDB and 1PDB. As per Oracle document:- https://docs.oracle.com/en/database/oracle/oracle-database/12.2/upgrd/deprecated-features-oracle-database-12c-r2.html#GUID-5D181F03-F74D-4888-B7B2-7176CF6FA8F8 Deprecation of Non-CDB Architecture The non-CDB architecture was deprecated in Oracle Database 12c. It can be desupported and unavailable in a release after Oracle Database 19c . Oracle recommends use of the CDB architecture. Oracle Database 19c ? Release 12.2: Ne...