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 Consulting

The Data Warehouse Development Life Cycle

Oracle Features for the Data Warehouse

Oracle’s Table CACHE Option

When Oracle manages I/O against the database, it uses different rules about where new data blocks are placed in the buffer cache. For all I/O’s except full-table scans, rows are read into the most-recently-used section of the Oracle buffer pool. As new data blocks are fetched, the older blocks work their way down to the least-recently-used end of the buffer, where they are eventually erased from the buffer to make room for newly acquired data blocks. (Figure 8.2)

Figure 8.2 Aging blocks from the Oracle buffers

The exception to this rule are data blocks that are acquired by using full-table scans. As data blocks are read into the buffer, blocks are placed on the opposite end of the buffer, in the least-recently-used option of the buffer. In this fashion, full table scans will not interfere with buffers on the most-recently-used end of the buffer (i.e. rows from non-full-table-scan transactions). Since these rows are already at the least-most-recently used end of the buffer, they will be flushed quickly as new rows are fetched as part of the full-table scan. (Figure 8.3) As we may know, full-table scan data blocks are physically read into Oracle’s buffer in chunk sizes that are specified by the init.ora parameter DB_FILE_MULTIBLOCK_READ_COUNT. For example, assume that the DB_BLOCK_SIZE is set to 8192 bytes (8K) and the DB_FILE_MULTIBLOCK_READ_COUNT is set to 8. When Oracle detects a full-table scan, Oracle will perform reads of four physical blocks at a time, pulling in 64K with each I/O. Remember, physical I/O is very time consuming, and anything that can be done to reduce I/O will improve Oracle performance.

Figure 8.3 Different ends of the buffer cache may be used for different tables


This is an excerpt from "High Performance Data Warehousing". To learn more about Oracle, try "Oracle Tuning: The Definitive Reference", by Donald K. Burleson.  You can buy it direct from the publisher at 30% off here:
http://www.rampant-books.com/book_1002_oracle_tuning_definitive_reference_2nd_ed.htm
 

 


Expert Remote DBA

BC is America's oldest and largest Remote DBA Oracle support provider.  Get real Remote DBA experts, call
BC Remote DBA today.

 

 

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.