Clarification of DSPFD output

When you do a DSPFD on a file on the there is some info that I need
clarification on.
I have a file that says the following..

Open Operations......................................77,875
Close Operations......................................77,875
Write Operations.......................................16,940
Update Operations....................................0
Delete Operations.....................................16,940
Logical Reads........................................513,079,190
Physical Reads......................................201,016,762


This is a highly volitile file used for passing trigger info around and I
understand the Open Closes and Write/Update/Delete numbers.
What do the Logical and Physical reads mean. This is an unkeyed physicalwith
no logicals etc.

krisV
______________________________________
THIS DOCUMENT IS PROVIDED FOR INFORMATIONAL PURPOSES ONLY.  The information
contained in this document did represent the current view of Kris
Vaidyanathan on the issues discussed as of the date of publication.  Because
Kris Vaidyanathan must respond to changes in reality, space time phenomena
and local subspace conditions, it should not be interpreted to be a
commitment on the part of Kris Vaidyanathan and Kris Vaidyanathan cannot
guarantee the accuracy of any information presented after the date of
publication..(this does not mean that I am an idiot.)
INFORMATION PROVIDED IN THIS DOCUMENT IS PROVIDED 'AS IS' WITHOUT WARRANTY
OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
FREEDOM FROM INFRINGEMENT...(this sounds great. If you figure it out, do
tell me what it means)
The user assumes the entire risk as to the accuracy and the use of this
document. This  document may be copied and distributed subject to the
following conditions:
1.   All text must be copied without modification and all pages must be
included
2.   All copies must contain Kris Vaidyanathan's copyright notice and any
other notices provided therein
3.   This document may not be distributed for profit or for cheap laughs.



krishnan@ozemail.com.au
http://www.ozemail.com.au/~krishnan



+---
| This is the Midrange System Mailing List!
| To submit a new message, send your mail to MIDRANGE-L@midrange.com.
| To subscribe to this list send email to MIDRANGE-L-SUB@midrange.com.
| To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---