Second Level Support
Trace Table Entries
An SCP that supportslUCY communications functions correctly in a virtual
machine generated by a CP system that supportslUCY. The lUCY macro instruction generates an operation exception in the real
hardware.
When a virtual machine invokes anlUCY function, it must be in a virtual supervi
sor state.
A virtual machine must invoke the DECLARE BUFFER function before otherlUCY functions except the QUERY function. Failure to do so causes an operation
exception to be reflected to the virtual machine.
Thus, an SCP can supportlUCY in a virtual machine exactly as it does on real
hardware.
CP system code invokeslUCY functions through a CALL linkage rather than the lUCY macro instruction. lUCY support generates a trace table entry for each lUCY function. There is one
trace table entry type forlUCY entries (X'lS'). Each entry contains a subtype
field to indicate the exactlUCY function a communicator invoked.
Whether invoked from a virtual machine or from CP system code, all uses oflUCY are recorded in the CP trace table. The address portion of the old PSW is recorded
as part of the entry. A bit in the flags byte indicates whether this address is a real
address (when invoked fromCP) or a virtual address (when invoked from a virtual
machine). For virtual machine addresses, the address of the associatedVMBLOK can be obtained from preceding trace table entries.
ThelUCY trace facilities can be suppressed at assembly time by setting
&TRACE(9) to0 or at execution time by setting the X'80' bit to 0 in TRACFLG3
inPSA. lUCY functions invoked by other functions are also recorded as if they had been
invoked fromCPo These secondary functions include:
The RETRIEVE BUFFER function generates a SEVER for all established
paths.
The SEVER function generates a REJECT for each incoming outstanding
message and aPURGE for each outgoing outstanding message.
ACONNECT issued to a CP system service passes control to that service.
The selectedCP system service usually invokes the ACCEPT function.
TheCP dispatcher invokes the DESCRIBE and TEST COMPLETION func
tions to dequeue messages intended for theCP system. Inter-User Communications Vehicle 117
Trace Table Entries
An SCP that supports
machine generated by a CP system that supports
hardware.
When a virtual machine invokes an
sor state.
A virtual machine must invoke the DECLARE BUFFER function before other
exception to be reflected to the virtual machine.
Thus, an SCP can support
hardware.
CP system code invokes
trace table entry type for
field to indicate the exact
Whether invoked from a virtual machine or from CP system code, all uses of
as part of the entry. A bit in the flags byte indicates whether this address is a real
address (when invoked from
machine). For virtual machine addresses, the address of the associated
The
&TRACE(9) to
in
invoked from
The RETRIEVE BUFFER function generates a SEVER for all established
paths.
The SEVER function generates a REJECT for each incoming outstanding
message and a
A
The selected
The
tions to dequeue messages intended for the