The things I learned installing VM/BATCH 1.1.1
 
Program Product number is 5664-364.
 
Manuals are
  SC34-4093-1   VM Batch Facility
                Installation, Customization, and Administration
  SC34-4094-1   VM Batch Facility
                User's Guide
 
The batch monitor VM (BATCH) uses IUCV to communicate with the
batch worker VMs (BATCH1-n).
 
WAKEUP uses VMCF to trap SMSG's.
 
 
     |             | External  |     |
     | Instruction | Interrupt | CR0 |
     | To invoke   | Code      | Bit |
-----+-------------+-----------+-----|
IUCV | B2F0 rddd   | 4000      | 30  |
VMCF | Diag 68     | 4001      | 31  |
 
  When using the IUCV instruction, register 0 has the IUCV operation
code in it and rddd (the second half of the instruction) is the
base register and displacement of your IUCV buffer.  The codes in R0
aren't documented anywhere.  I saw what they were by looking at the
CP IUCV macro.  They are (in decimal)
     0 = QUERY      1 = TESTMSG    2 = RTRVBFR    3 = DESCRIBE
     4 = SEND       5 = RECEIVE    6 = REPLY      7 = TESTCMPL
     8 = REJECT     9 = PURGE     10 = ACCEPT    11 = CONNECT
    12 = DCLBFR    13 = QUIESCE   14 = RESUME    15 = SEVER
    16 = SETMASK   17 = SETCMASK
The IUCV buffer is well documented in the appropriate CP book that
describes IUCV.
 
  When you use the CMSIUCV macro, DMSIUC gets control, gets some free
storage for an IUCV buffer, and tells CP about it via a IUCV DCLBFR
request.  The anchor for that buffer is in the IUCVTAB, whose anchor
is AIUCVTAB (E64 in NUCON).  When an IUCV interrupt comes in, CP uses
CMS's buffer and CMS then moves the data into the application's buffer.
You can see what the interrupt is by
 
                   TRACE EXT
If 1A.2 = x'4000', D E64        to get AIUCVTAB (let's say it's at 3B30)
                   D 3B3C       to get anchor for IUCV buffer (1E9EB8)
                   D 1E9EB8.28  to get IUCV buffer.
 
The IUCV buffer is mapped by the IPARML DSECT.  At +3 is IPTYPE, which
tells you the type of interrupt it was.  See the appropriate CP book
for the possible external interrupt types and their explanation.