Index_Manager

About Indexes

Oracle Database provides several indexing schemes that provide complementary?performance functionality. These are:
1. B-tree indexes: the default and the most common
2. B-tree cluster indexes: defined specifically for cluster
3. Hash cluster indexes: defined specifically for a hash cluster
4. Global and local indexes: relate to partitioned tables and indexes
5. Reverse key indexes: most useful for Oracle Real Application Clusters applications
6. Bitmap indexes: compact; work best for columns with a small set of values
7. Function-based indexes: contain the precomputed value of a function/expression
8. Domain indexes: specific to an application or cartridge.

Guidelines for Managing Indexes

This section discusses guidelines for managing indexes and contains the following?topics:

1.?Create Indexes After Inserting Table Data

Data is often inserted or loaded into a table using either the SQL*Loader or an import?utility. It is more efficient to create an index for a table after inserting or loading the?data. If you create one or more indexes before loading data,the database then must?update every index as each row is inserted.

Creating an index on a table that already has data requires sort space. Some sort space?comes from memory allocated for the index creator. The amount for each user is?determined by the initialization parameter SORT_AREA_SIZE. The database also swaps?sort information to and from temporary segments that are only allocated during the?index creation in the user’s temporary tablespace.

Under certain conditions,data can be loaded into a table with SQL*Loader direct-path?load and an index can be created as data is loaded.

Index the Correct Tables and Columns

Use the following guidelines for determining when to create an index:

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