The database user specifies a table by entering its name. The table is accessed internally using a table ID of a fixed length.
The relationship between the table name and this table ID is stored in the database catalog.
In addition, the database system has a special management structure (file directory), in which the root pages of B* trees are assigned to table IDs.
The table IDs are stored in the file directory together with a type flag and other information. The type flag specifies whether the table contains primary data, secondary key , or LONG data. The type flag specification enables one table ID to be used for all the B* trees required for the logical structures of the same table.