SVCTRACE SVCTRACE Use the SVCTRACE command
supervisor calls occurring SVCTRACE command is:
to trace and record
in your virtual information about
The format of the r- 1 I SVCTrace , I , L- ON starts tracing all SVC instructions issued within OFF stops SVC tracing.
1. The trace information recorded on the printer includes: • The virtual storage location of the calling SVC instruction and
the name of the called program or routine • The normal and error return addresses • The contents of the general registers both before the SVC-called program is given control and after a return from that program • The contents of the general reqisters when the SVC handling
routine is finished processing • The contents of the floating-point registers before the SVC-called program is given control and after a return from that
program • The contents of the floating-point registers when the SVC handling routine is finished processing • The parameter list passed to the SVC 2. To terminate tracing previously established by the SVCTRACE command, issue the HO or SVCTRACE OFF commands. SVCTRACE OFF and HO cause all trace information recorded, up to the point they are
issued, to be printed on the virtual spooled printer. On typewriter terminals SVCTRACE OFF can be issued only when the
keyboard is unlocked to accept input to the command
environment. To terminate tracing at any other point in system HO must be issued. To suspend tracing temporarily
during a session, interrupt processing and enter the Immediate
command SO (Suspend Tracing). To resume tracing that was suspended
with the SO command, enter the Immediate comMand RD (Resume
Tracing) .
If you issue the CMS Immediate command HI or you log off the VM/370 system before termination of tracing previously set by the SVCTRACE command, the switches are cleared automatically and all
recorded trace information is printed on the virtual spooled
printer.
If a user timer exit is activated while SVCTRACE is SVCTRACE is disabled for the duration of the timer exit.
issued during the timer exit are not reflected in the
listing.
active,
Any SVCs SVCTRACE Section 2. Commands 179

SVCTRACE 3. When tracing on a virtual machine with only one printer, the trace
data is intermixed with other data sent to the virtual printer.
A variety of information is printed whenever the: SVCTRACE ON command is issued.
The first line of trace output starts with a dash or plus sign or an
asterisk (-or + or *l. The format of the first line of trace output
is:
N/D = xxx/dd name loc OLDPSW = psw1 GOPSW = psw2 [RC=rc]
indicates information recorded before processing the SVC. + indicates information recorded after processing the SVC, unless
the asterisk (*) applies.
* indicates information recorded after processing a eMS SVC that
had an error return.
N/D
xxx
dd
name
loc
pswl
psw2
rc
is an abbreviation for SVC number and depth (or level).
is the number of the SVC call (they are numbered sequentially) is the nesting level of the SVC call.
is the macro or routine being called.
is the program location from which the SVC was issued.
is the PSW at the time the SVC was called.
is the PSW with which the routine being called is invoked, if
the first character of this line is a dash (-) If the first
character of this line is a plus sign or asterisk (+ or *), PSW2 represents the PSW that returns control to the user.
is the return code from the SVC handling routine in general
register 15. This field is omitted if the first character of
this line is a dash (-), or if this is an JS SVC call. For a CMS SVC, this field is 0 if the line begins with a plus sign
(+), and nonzero for an asterisk (*). Also, this field equals
the contents of R15 in the "GPRS AFTER" line.
The next two lines of output are the
registers when control is passea to the SVC output is identified at the left by ".GPRSB". is:
contents of the general
handling routine. This
The format of the output .GPRSB = h h h h h h h h *daaadddd* h h h h h h h h *daaddddd* 1BO VM/370 CMS Command and Macro Reference