One small correction. The bit/error/whatever is not for "Unicode Services 
Available" but for "CUNLINFO available." 

CUNLINFO is not "essential" (unless particular program logic treats it as so). 
CUNLINFO lets a program detect translation parameter mismatches ahead of doing 
any actual translation. The product I am responsible for survives a return code 
saying that CUNLINFO is not available by putting out a message at parameter 
validation time that if the specified translation is wrong, you won't know it 
until the program attempts an actual translation.

CUNLINFO was an addition to Unicode Services around V1R10. My code was written 
when V1R9 was still common; that's why I coded it that way. Validate parameters 
if possible; else just inevitably blow up at translation time.

Charles

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf 
Of J O Skip Robinson
Sent: Thursday, October 15, 2015 8:06 PM
To: [email protected]
Subject: Re: (External):Re: Unicode services Red alert

I'm piecing together various clues. It appears to me that:

1. The UCCB is a defined control block, mapped in several (!) MACLIB members 
such as CUNBAIDF. 
2. Various flags are defined beginning at UCCB+10.
3. Somehow during IPL the system clock has been overlaying UCCB+10 by 
(presumably) Unicode set up processing.
4. No one noticed all this time because the flag nibble in the timestamp has 
always, coincidentally, indicated 'Unicode available'.
5. As of the magic moment on December 15, the clock rolls over and reverses the 
benign bit. Without the fix, Unicode appears to be unavailable more or less 
forever. Until the bit once again changes back?

I suspect that checks for the timestamp are far rarer than checks for Unicode 
availability. So the fix is to store the clock somewhere else at IPL (UCCB+20) 
and ensure that the critical flags are zero. Our PMR indicates what I 
suspected: a zero value means OK, a one value means not OK. This is analogous 
to the RACF flag in the CVT. Zero means that RACF is functional while one means 
that it is not. I have a hilarious war story about how I know that. 

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