Re: origin of CHAIN

["Todd Sabella" <Todd.Sabella@xxxxxxxxxx>]

     Paraphrased from my RPGII book...
     
     Back in the days of having transaction files update ISAM 
     (Indexed-Sequential Access Method) disk files, the transaction file is 
     called the Chaining File and the ISAM disk file is called the Chained 
     File.
     
     Chained files are normally master disk files such as customer master 
     files or inventory master files.
     
     The field from the chaining file, which contains the key field values, 
     is called the chaining field.  This field must have a value the same 
     type and size as the keys stored in the index of the ISAM file and 
     individual records.  The key fields stored in the index and ISAM 
     records are called the chained fields.
     
     For example, customer number on the transaction file and customer 
     number in the master file.
     
     On the F-spec of the ISAM file, you had to tell the compiler that the 
     ISAM file was a chaining file and that it was to be randomly 
     processed.
     
     The opcode CHAIN was named because it performs the chaining functions 
     in the RPGII compiler.
     
     
______________________________ Reply Separator _________________________________
Subject: origin of CHAIN
Author:  RPG400-L@midrange.com at INTERNET 
Date:    7/6/2001 2:01 PM
     
     
My co-worker today had an interesting (and on topic!) question:  Where did 
CHAIN originate?  In the RPG manual chain is listed as retrieve random 
record.  We couldn't figure out how that translates to sound like chain. 
It sounds like the opcode should have been RTVREC or something.  Anyone 
know the history?
     
James Rich
james@eaerich.com
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