iX V6.5 (30391-90011)

Chapter 11 491

B-Tree Indices

Overview of B-Tree Indices

11 B-Tree Indices

This chapter is new with the release which includes the enhancement to support B-Tree

indices (C.07.00). This chapter gives an overview of the B-Tree index enhancement. It

addresses changes in TurboIMAGE/XL utilities and intrinsics, and presents a quick start

for using B-Tree indices.

This chapter has the following major sections:

• Overview of B-Tree Indices

• External Commands and Utilities Affected

• Limits

• Quick Start for Using B-Tree Indices

Overview of B-Tree Indices

An index on an item allows generic and range searches. To optimize the search of an index,

a technique commonly know as "Binary Tree Searching" is used. Hence, the name B-Tree

index is used to refer to an index in TurboIMAGE/XL.

You can create a B-Tree index only on the master data set's key item. Nevertheless, you

are able to perform index searches using all of its corresponding detail data set search

items as well. A master data set key item is perceived as having an explicit B-Tree index

and all of its corresponding detail data set search items are perceived as having implicit

B-Tree indices. The index searches are done using DBFIND. If you create an index on a key

item of the master data set, you can use this master data set in the DBFIND intrinsic.

Terminology

Explicit B-Tree index is an index actually created on the key item of the master

data set. The index searches can be done using this key

item in the DBFIND intrinsic.

Implicit B-Tree index is an implied index, which does not physically exist, but

index search is allowed on the detail data set search item

whose corresponding master data set key item has a

B-Tree index.

B-Tree DBFIND is a DBFIND on a master or detail data set using a key

item or a search item that has a B-Tree index (explicit or

implicit). For a master set, it is a set of entries in the

master which satisfy the DBFIND criteria. For a detail

data set, DBFIND is also referred to as a super-ﬁnd

which locates a set of master data set entries, all of which