Explanation/Reference:
Explanation:
D: The database internally uses standard file system interfaces to create and delete files as needed for the following database structures:
Tablespaces

Redo log files

Control files

Archived logs

Block change tracking files

Flashback logs

RMAN backups

Note:
* Using Oracle-managed files simplifies the administration of an Oracle Database. Oracle-managed files eliminate the need for you, the DBA, to directly manage the operating system files that make up an Oracle Database. With Oracle-managed files, you specify file system directories in which the database automatically creates, names, and manages files at the database object level. For example, you need only specify that you want to create a tablespace; you do not need to specify the name and path of the tablespace's datafile with the DATAFILE clause.
References: http://www.oracle-base.com/articles/9i/oracle-managed-files.php
http://docs.oracle.com/cd/B10500_01/server.920/a96521/omf.htm