Solved

logical vs physical reads

Posted on 2006-11-16
6
933 Views
Last Modified: 2008-03-17
what is the difference between logical reads and physical reads?
0
Comment
Question by:yanci1179
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
  • 2
6 Comments
 
LVL 143

Accepted Solution

by:
Guy Hengel [angelIII / a3] earned 300 total points
ID: 17959845
physical reads means the data has been read from disk into memory
logical reads means the the data was already in memory

1 logical reads means 1 page of data, ie 8KB
0
 

Author Comment

by:yanci1179
ID: 17959911
i read that in books online....but it didn't really mean much.  Ideally which one should be lower?
0
 
LVL 32

Assisted Solution

by:bhess1
bhess1 earned 200 total points
ID: 17959980
In a perfect world, physical reads would be equal to the number of data blocks in your database, and all other reads would be logical.  So, by preference logical reads should be the higher of the two.
0
Salesforce Made Easy to Use

On-screen guidance at the moment of need enables you & your employees to focus on the core, you can now boost your adoption rates swiftly and simply with one easy tool.

 
LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 17960495
perfectly, the physical reads should be 0. also, logical reads as low as possible.
0
 

Author Comment

by:yanci1179
ID: 17960572
let me see if I understand this logical data read from what is already in cache.  if it's not there then it has to read the physical tables and retrieve the data?
0
 
LVL 32

Expert Comment

by:bhess1
ID: 17962141
Absolutely correct.
0

Featured Post

Get 15 Days FREE Full-Featured Trial

Benefit from a mission critical IT monitoring with Monitis Premium or get it FREE for your entry level monitoring needs.
-Over 200,000 users
-More than 300,000 websites monitored
-Used in 197 countries
-Recommended by 98% of users

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article shows gives you an overview on SQL Server 2016 row level security. You will also get to know the usages of row-level-security and how it works
A Stored Procedure in Microsoft SQL Server is a powerful feature that it can be used to execute the Data Manipulation Language (DML) or Data Definition Language (DDL). Depending on business requirements, a single Stored Procedure can return differe…
Familiarize people with the process of utilizing SQL Server functions from within Microsoft Access. Microsoft Access is a very powerful client/server development tool. One of the SQL Server objects that you can interact with from within Microsoft Ac…
Viewers will learn how to use the SELECT statement in SQL to return specific rows and columns, with various degrees of sorting and limits in place.

690 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question