An Oracle database is made up of physical and logical structures. Physical structures are those that can be seen and operated on from the operating system, such as the physical files that store data on a disk.

Logical structures are created and recognized by Oracle Database and are not known to the operating system. The primary logical structure in a database, a tablespace, contains physical files. The applications developer or user may be aware of the logical structure, but is not usually aware of this physical structure. The DBA must understand the relationship between the physical and logical structures of a database.

Figure 6-1 shows the relationships between logical and physical structures. This figure also shows recovery-related structures that are optionally kept in the flash recovery area. See "Flash Recovery Area" for more information.