"l!I I .... .... IQ C t1 (I) H tu ::a ca til n ........ W -..l H 0 t:I .... tn f+ .... rn PI f+ .... (I) .... • N PI I:'"' f+ 0 .... IQ 0 .... t:I n PI t:I QI t1 0 tr .... (I) • (I) f+ (I) t1 • .... t:I PI .... 0 t:I I I ca 0 .... i CD INPUT VMBLOK D Ej INPUT I-OLlSJ B PROCESS------ IT OM"CKP '0 X'SOO' DMKCKP
For a warm start II: '....,k"'o .. ''' .. "" "'''0' U "d.'m ,,,,,m '" m''''g' ' ijdOMKSAV DMKSAV (DMKSAVRS Read copy of nucleus entry point) D '.0".' ,. OMKcP' If p;.:::-==-:-:------­ DMKAPI t rocessor call functions. 0 perform initialization Initialize storage and
Mount devices check TOO clock
Log on operator Allocate Dump File start, perform that function
Go to Dispatcher
Wait for work r-----:------­ System's !ables

The real machine configuration is represented by
a set of related 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 one control 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) is I ,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, that value 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, that value is
an index to RDEVBLOK 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 the RDEVBLOK is used
in the same way for all devices. However, some of the. fields in the RDEVBLOK have multiple uses, depending
on the device type and function.