The DEFINE, DELETE, DISCONN, QUERY, and STARl commands are processed
entirely by the system control task, as theymay involve the referencing
and updatingof the system status tables (DMTSYS). For the CHANGE, PURGE, and ORDER commands, £MTCMX builds a formatted
table called a command elementand passes it, via an ALERT request, to
theDMTAXS task for execution.
TheBACKSPAC, CMD, DRAIN, HOLD, MSG, and TRACE commands are passed to the line driver task for the associated active
link via a command element and ALERT request.
Rses MessageHandling Messages can occur in response to a command or sFontaneously as a result
of a system malfunction.
The task that originates the message
the variable portion of the message textDMTMGX obtains the fixed portion of
information from theDMTMSG module, and
appropriate operator.
passes the message number and
to the message handler,DMTMGX. the message text and routing
then issues themessage to the
Messages can be addressed to the localRSCS operator, remote station
operator, localVM/370 virtual machine, VM/370 system operator, or
combinations of these.Messages directed to the VM/370 system operator or VM/370 user are
issued via the CPMSG command using the virtual console function of the DIAGNOSE interface. Messages for the local RSCS operator are enqueued
for output byDMTREX. Messages for the remote station operator are
presented to the line drivers for the associated links via anRSCS MSG command element and ALERT request. Interruption Handling Three types of interruptions are handled
routines: external interruptions,SVC interruptions. EXTERNAL INTERRUPTIONS by the supervisor service
interruptions, and I/O
External interruptions are handled by theDMTEXT module. Each bit cf
the external interruption code (bytes 16-31 of the external oldPSW in
low storage) is inspected.When a bit is set to one, a scan of the
external exit requestqueue is made to locate the first requested exit
for the bit that was set. If one is found, the exit is taken;
otherwise, processing continues until the entire interruption code has
been inspected.
338IBM VM/370 System programmer's Guide
entirely by the system control task, as they
and updating
table called a command element
the
The
link via a command element and ALERT request.
Rses Message
of a system malfunction.
The task that originates the message
the variable portion of the message text
information from the
appropriate operator.
passes the message number and
to the message handler,
then issues the
Messages can be addressed to the local
operator, local
combinations of these.
issued via the CP
for output by
presented to the line drivers for the associated links via an
routines: external interruptions,
interruptions, and I/O
External interruptions are handled by the
the external interruption code (bytes 16-31 of the external old
low storage) is inspected.
external exit request
for the bit that was set. If one is found, the exit is taken;
otherwise, processing continues until the entire interruption code has
been inspected.
338