Each table in the database has a table ID of a fixed length, which gives the table a unique identity. The database system uses the table ID to access a table. To access a table with an SQL statement, you need to specify the table name.
The allocation of the table name to the table ID is stored in the database catalog; the allocation of the table ID to the B* trees is stored in the internal file directory.
Concepts of the Database System, Logical Access Structures