#keyfrom

Unpacking a PL/I VSAM keyed write loop.

I found myself faced with the task of understanding the effects of a PL/I WRITE loop that does the initial sequential load of a VSAM DATASET.  The block of code I was looking at had the following declarations:

dcl IXUPD FILE UNBUFFERED KEYED env(vsam); dcl 01 recArea, 03 recPrefix, 05 recID PIC'(4)9' init (0), 05 recKeyC CHAR (4) init (' '), 03 recordData CHAR (70) init (' '); dcl recIndx FIXED…