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Difference between physical sequence and logical sequence


IBM Mainframe Forums -> DFSORT/ICETOOL
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sairam_12_06

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Joined: 05 Apr 2006
Posts: 2

PostPosted: Sun Apr 09, 2006 9:51 pm
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pl. explain the difference between physical sequence and logical sequence of records in a file.
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DavidatK

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Joined: 22 Nov 2005
Posts: 700
Location: Troy, Michigan USA

PostPosted: Tue Apr 11, 2006 2:07 am
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sairam_12_06,

I believe the difference can probably be seen best in a keyed indexed file.

Say you have a file of members of this forum with Name, date joined Indexed by Name

Entries are:

(physical
Record) Name / Join Date

(Rec 1) Mcmillan / 2003-05-18
(Rec 2) Mmwife / 2003-05-30
(Rec 3) Anuradha / 2004-01-06
(Rec 4) Iknow / 2005-08-22
(Rec 5) DavidatK / 2005-11-22
(Rec 6) sairam_12_06 / 2006-05-05

If you look at the file physically sequentially, you will see the records actually how they are physically on the file, one after the other, in the order they were entered into the file

(rec 1) Mcmillan
(rec 2) Mmwife
(rec 3) Anuradha
(rec 4) Iknow
(rec 5) Davidatk
(rec 6) Sairam_12_06

But, if you want to look at them in a Name logical sequential order, you will see the records, one after the other, not how they are physically on the file, but in a logical name order, from the Name index.

(rec 3) Anuradh
(rec 5) DavidatK
(rec 4) Iknow
(rec 1) mcmillan
(rec 2) mmwife
(rec 6) sairam_12_06

Dave
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