A B+ tree is a data structure in which records associated 
with the search keys are at the leaves of the tree.This 
provide efficient retrieval,insertion and removal of 
records.Keys are triplicale to the non-leaf nodes to 
provide a path to the searched record.
NT file system,JFS2 file system and Rationaldata base often 
used this data structure for indices.

a B+ tree is a type of tree which represents sorted data in
a way that allows for efficient insertion, retrieval and
removal of records, each of which is identified by a key. It
is a dynamic, multilevel index, with maximum and minimum
bounds on the number of keys in each index segment (usually
called a 'block' or 'node'). In a B+ tree, in contrast to a
B-tree, all records are stored at the lowest level of the
tree; only keys are stored in interior blocks.

The primary value of a B+ tree is in storing data for
efficient retrieval in a block-oriented storage context.
Given a storage system with a block size of b, a B+ tree
which stores a number of keys equal to a multiple of b will
be very efficient when compared to a binary search tree (the
corresponding data structure for non-block-oriented storage
contexts).