The database system creates the following B* trees for LONG columns:
· A B* tree for the primary data (primary tree), sorted by primary key
· A B* tree for the short values in the LONG column
LONG values that are shorter than one page are also known as short LONG values or short column file. LONG values that are longer than one page are also known as long LONG values.
· An additional B* tree for each long LONG value in the LONG column
The leaf pages of the primary tree for the values of the LONG column contain either links to the short column file or the table ID of a long LONG B* tree.
The following figure shows the B* trees for a base table with a LONG column, which contains both short LONG and long LONG values.