Figure 4. CMS Co •• and (and Request) Processing Notes
Pass contfol to the routine !In the nucleus. userarea'toe.ecute the command
1. If the terminal line was actually from an EXEC file, or if the
command SET IMPEX OFF has been executed, implied EXEC is not In effect.
2. A -3 return code md,cates SVC 202 processing did not find
the command.
3. If the terminal hne was actually from an EXEC file, or if the
command SET IMPEX OFF has been executed, implied CP 15 not In effect.
2-30 IBM VM/370 System Logic and Program Determination--Volume 2

CALLED ROUTINE START-UP TABLE
Figures 5 and 6 show how the PSW and registers are set up when the
called routine is entered.
r I "Called" Type System Mask 1--------------- ISVC 202 or 203 Disabled I - Nucleus I resi1ent 1--------------- -------------- ISVC 202 or 203 - Transient
area MODULE SVC 202 or 203 - User area User- handled
as - DOS/VS Nucleus
resident
as - DOS/VS Transient
area module
Disabled
Enabled
Enabled
Disabled Storage Key Problem Bit System Off User Off User Off User Off System Off System Off Figure 5. PSW Fields When Called Routine Starts
,
Registers RegisterslRegisterlRegister RegistertRegisterl
Type o -1 2 -11 1 12 I 13 14 I 15 I I I 1 I SVC 202 Same as Unpre- IAddress IUser Return 'Address I or 203 caller dictable I of I save address' of I I called I area to I called I , routine I , routine I ----I I I I other Same as Same as IAdd ress IUser Return ISame as I caller caller I of I save address I caller , 1 caller , area to , 1 I I I I Figure 6. Register Contents When Called Routine Starts RETURNING TO THE CALLING ROUTINE When the called routine finishes processing, control is returned to DMSITS, which in turn returns control to the calling routine.
The return is accomplished by leading the original SVC old PSi (which
was saved at the time DMSITS was first entered), after possibly modifying the address field. The address field modification depends upon the type of SVC call, and upon whether or not the called routine
indicated an error return. eftS Introduction 2-31