DMSNUC USERSECT SUBSECT OPSECT DMSABW DMSFRT DMSERT DBGSECT (Debug work areal CVTSECT(Some fields are filled in
at IPl.) FVS DIOSECT SVCSECT PGMSECT IOSECT EXTSECT AFTSECT (Create when the file is
opened. There is room for 5 AFTs in DMSNUC, others are in free storage. ADTSECT (Space is allocated when DMSNUC is assembled, fields are filled in when ACCESS command is
issued. There is one ADT entry for
each of the 10 possible disks.)
DEVTAB
Terminal Buffers and Saveareas NUCON Figure 12. CMS Control Blocks COLLECT INFORMATION CMSCB DCB DECB I eM'AVE I B Examine several other fields in NUCON to analyze the status of the CftS system. As you proceed with the dump, you may return to NUCON to pick up
pointers to specific areas (such as pointers to file tables) or to
examine other status fields. The complete contents of NUCON and the
other CMS control blocks are described in the The following areas of NUCON may contain useful
debugging information.

April 1, 1981 e Save Area for Low Storage executing, DEBUG saves the first 160 bytes of low storage in a NUCON field called LOWSAVE. LOWSAVE begins at X'CO'. • Register Save Area DMSABN, the abend routine, saves the user's floating-point and
general registers. Kielg FPRLOG GPRLOG ECRLOG • Device 1ocati2!! X'160' X'1S0' X'1CO' contents User floating-point registers User general registers User extended control registers
The name of the device causing the last I/O interrupt is in the DEVICE field at X'26C'. • Last Two Commands or procedures Executed Figlg LASTCMND PREVC!1ND LASTEXEC PREVEXEC 1Qcati2!! X'2AO' X'2A'S' X'2BO' X' 2BS' Last CMS command issued
Next to last CMS command issued
Last EXEC procedure invoked
Next to last EXEC procedure invoked • Last Module Loaded into Free Storage and the Transient Area
The name of the last module loaded into free storage via a LOADMOD is
in the field LASTL!10D (location X'2CO'). The name of the last module
loaded into the transient area via a LOADMOD is in the field LASTTMOD (location X'2CS'). • Pointer to CMSCB The pointer to the CMSCB is in the FCBTAB field located at X'SCO'. CMSCB contains the simula·ted as control blocks. These simulated as blocks are in free storage. The CMSCB contains a PLIST for CMS 1/0 functions, a simulated Job File Control Block (JFCB), a
simulated Data Event BlocK (DEB), and the first in a chain of I/O Blocks (lOBs). • The Last Command
The last command entered from the terminal is stored in an area
called CMNDLINE (X'7AO'), and its corresponding PLIST is stored at CMNDLIST (X'S4S'). • Interrupt Work Area EXTSECT (X'1SS0') is a work area for the external interrupt handler.
It contains: The PSW, EXTPSW (X'1SFS') Register save areas, EXSAVE1 (X'1SBSI) separate area for timer interrupts, EXSAVE (X'1SS0') Part 1. Debugging with VM/370 71