Migrating Dictionary Managed Tablespace To Locally Managed Tablespace

 Migrate a dictionary managed SYSTEM tablespace to locally managed :

SQL> DBMS_SPACE_ADMIN.TABLESPACE_MIGRATE_TO_LOCAL          ('SYSTEM');

Use the below following steps to convert your SYSTEM tablespace from Dictionary Managed to locally Managed :

• Make a complete backup of your Database
• Ensure that the database has a default temporary tablespace that is not SYSTEM. The temporary tablespace is created using the CREATE TEMPORARY TABLESPACE command.
• Eliminate any undo (rollback) segments in disctionary-managed tablespaces.
• There should be at least one online undo segment in a locally managed tablespace, or an undo tablespace should be online.
• All tablespaces other than the tablespace containing the undo space and the default temporary tablespace should be placed in READ ONLY mode.
• Startup the instance in restricted mode.
• Migrate the SYSTEM tablespace by using the above command.

Note: Any non-SYSTEM dictionary managed tablespace that is not migrated to locally managed prior to migrating the SYSTEM tablespace, cannot be altered to READ-WRITE. The tablespace will remain READ-ONLY. Only locally managed tablespaces can be altered to READ-WRITE after the migration of the system tablespace.

Thank you !!