The real machine configuration is represented by
a set ofrelated control blocks. These blocks are: • in the VM/'nO nucleus • built from macros during system generation • loaded at system IPL and initialized then for
operation.
There is onecontrol block per channel, per control unit, and per device. The characteristics of VM/370 real I/O control are: • Block multiplexing (BMPX) with RPS (Rotational Position
Sensing) isI ,sed. • Multi-path ·;cheduling is not used. • All I/O operations are handled by VM/370 scheduling iJnd interrupt handling. .6 DMKRIOCT - real channel table
l - . - indicates that no channel exists -positive value is an index RCHBLOK - real channel block I Channel identification Scheduling Control to the RCHBLOK XXXX I Control Unit t---+--+--t-X-X-X-X-l Index Table unit exists
if positive, thatvalue is an hldex to the RCUBLOK RCUBLOK - real control unit block
l Control Unit identification Scheduling Control if negative (FFFF), no
device ex ists
XXXX
XXXX
if positive, thatvalue is
an index toRDEVBLOK e complete c:..crlptlon of CP control block •• _ IBM Virtual Mschine Fscility/3.70: Datil ArelU and Control Bloe"'. "'der No. SY20-0884. __ , __ _________________________ -J Device Index Table Relationship of R,eal I/O Control Blocks ---- DMKRIOCT (part of DMKIRIO) RCUBLOKs RDEVBLOKs Mn. t,-+--><-t-' IRDEVBl.OK - real device block' Device identification Scheduling Control Terminal Control Spooling Control Dedicated Control Error Recovery Allocation Control Part of the RDEVBLOK pertains to functions that are
device independent; that part of theRDEVBLOK is used
inthe same way for all devices. However, some of the. fields in the RDEVBLOK have multiple uses, depending
on the device type and function.
a set of
operation.
There is one
Sensing) is
l
if positive, that
l
device ex ists
XXXX
XXXX
if positive, that
an index to
device independent; that part of the
in
on the device type and function.