Wow! Unfortunate design indeed.

Alternatively you could probably zap it with a debugger, right? Running 
authorized, and typing very, very carefully. <g>

Charles


-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf 
Of Sam Golob
Sent: Tuesday, October 16, 2018 9:07 AM
To: [email protected]
Subject: Bad Design but nobody cares

Hi Folks,

     I hope this post isn't considered a waste of everyone's time.  I 
came across this "design element" (so to speak) in my work concerning 
the Broadcast Dataset (aka SYS1.BRODCAST, in its more restrictive sense).

     Question:  When you are reformatting the active Broadcast Dataset 
(SYS1.BRODCAST) with the SYNC command, you create space for 100 global 
Notices (the messages that everybody sees when they LOGON).  How do you 
change this number?

     Answer:  You probably would never want to change this number, 
because 100 notices is adequate for most purposes.  But what if you 
really DO want to change this number?  Then IBM tells you to zap a 
fullword field at the beginning of TSO initiation module IKJEFXSR, and 
re-IPL (maybe with CLPA, just to be safe).  Again, you'd probably never 
want to do this, because 100 notices is adequate for almost everyone.

     Where is that number (100, or F'64') kept?  It is actually a 
fullword in the CVT itself, at displacement X'5A8'. It is not "chained 
off the CVT".  It is actually a fullword IN the CVT...!!!!  Wow!

     So how would a fullword in the CVT be changed?  Presumably only at 
IPL time.  That's why IBM's method of changing it is so cumbersome, 
since (I think) IKJEFXSR, which starts up TSO, has to put that number 
into the CVT.

     Anyway, if someone REALLY wants to change this number (temporarily, 
for the duration of the IPL), I wrote an authorized TSO command called 
BDMNNOTC, which will take a number as a parameter, convert it to 

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