BC remote Oracle DBA - Call (800) 766-1884  
Oracle Consulting Oracle Training Development

Remote DBA

Remote DBA Plans  

Remote DBA Service

Remote DBA RAC

   
Remote DBA Oracle Home
Remote DBA Oracle Training
Remote DBA SQL Tuning Consulting
Remote DBA Oracle Tuning Consulting
Remote DBA Data Warehouse Consulting
Remote DBA Oracle Project Management
Remote DBA Oracle Security Assessment
Remote DBA Unix Consulting
Burleson Books
Burleson Articles
Burleson Web Courses
Burleson Qualifications
Oracle Links
Remote DBA Oracle Monitoring
Remote DBA Support Benefits
Remote DBA Plans & Prices
Our Automation Strategy
What We Monitor
Oracle Apps Support
Print Our Brochure
Contact Us (e-mail)
Oracle Job Opportunities
Oracle Consulting Prices





   

 

 

 

Remote DBA services

Remote DBA Support

Remote DBA RAC

Remote DBA Reasons

Remote Oracle Tuning

Remote DBA Links

Oracle DBA Support

Oracle DBA Forum

Oracle Disaster

Oracle Training

Oracle Tuning

Oracle Training

 Remote DBA SQL Server

Remote MSSQL Consulting

Oracle DBA Hosting

Oracle License Negotiation

 

 


 

 

 

 

   
  Oracle Tips by Burleson

Administration of Indexes

Indexes can make or break an application. A nonindexed query that takes tens of minutes can be made to return values within seconds if indexes are done properly. A critical subset of the Remote DBA’s tasks involves the placement, creation, sizing, and maintenance of the normal, bitmapped, partitioned, function-based, and subpartitioned indexes available in Oracle8, Oracle8i and Oracle9i.

Oracle8 offered new functionality in the form of partitioned, bitmapped, and reversed key indexes. Oracle8i offered all of these plus the capability to do INDEXTYPE, DOMAIN INDEX, and function-based indexes, as well as more advanced partitioning options for indexes. Partitioned indexes allow the spread of index data automatically by data value range across multiple partitions that can be placed on several disk arrays or platters. In Oracle8i, these partitions can be further subdivided into subpartitions. Bitmapped indexes allow for indexing of low-cardinality data, a feature that came about in 7.3.2.3 and continued with Oracle8 and its later releases. Bitmapped indexes map data values as binary integers, allowing low-cardinality data to be quickly accessed with sometimes almost quantum decreases in access speed. For some specialized types of query, a reverse key index can improve data access speeds.      

In Oracle9i, two new types of index are offered: the bitmap join index and the skip scan index. A bitmap join index acts as an intersection between two tables, in a sense, prejoining them via a bitmap index. A skip scan index is a specially constructed index that allows Oracle to scan independent B-tree levels instead of the normal top-down scan. Indexes allow queries to rapidly retrieve data, with proper implementation. Single columns, or groups of columns, can be indexed. A Remote DBA can specify whether or not an index is unique. Remember, for proper table design, each table must have a unique identifier. A unique index is automatically created when a unique or primary key constraint clause is used in a CREATE or ALTER TABLE command.      

Indexes speed the search for queries when approximately 2 to 7 percent of the table or less is being retrieved. For larger retrievals, inserts, and updates to index columns, and deletes, indexes slow response. An exception to this is if you use a bitmapped index for low-cardinality data.     

How columns are indexed affects their efficiency. Order columns should be specified to reflect the way a select will retrieve them. The column accessed most often should be put first. Remember, the leading portion of the index is used to speed queries. A composite index can be created on up to 16 columns. Columns of type LONG and LONG RAW cannot be indexed.

See Code Depot


www.oracle-script.com

Remote DBA Service
 

Oracle Tuning Book

 

Advance SQL Tuning Book 

BC Oracle support

Oracle books by Rampant

Oracle monitoring software

 

 

 

 

 

 

BC Remote Oracle Support

Remote DBA

Remote DBA Services

Copyright © 1996 -  2013 by Burleson. All rights reserved.

Oracle® is the registered trademark of Oracle Corporation.