DISPLAY

Purpose

Use the DISPLAY commands to see data from the following machine components, both real and virtual:
  • The contents of first-level (host) storage
  • The contents of second-level storage (the storage that appears real to the operating system running in your virtual machine)
  • The contents of third-level storage (the storage that appears virtual to the operating system running in your virtual machine)
  • The old and new PSWs, and interrupt information for the following interrupts:
    • SVC
    • I/O
    • PROGRAM
    • EXTERNAL
    • MACHINE CHECK
  • Storage keys
  • Linkage stack
  • The contents of these registers:
    • Access
    • Control
    • Floating-point
    • Floating-point control
    • General purpose
    • Prefix
  • Subchannel information blocks (SCHIBS)
  • The current program status word (PSW)

Usage Notes

(General for DISPLAY)

  1. Using a single command, you can display the contents of multiple storage locations, registers, and control words.

    Follow these rules to execute the command properly:

    1. Do not put blanks between operands that relate to a single DISPLAY request, except for PSW and SCHIB, which require at least one blank between the first and second operands. For example, if you want to display hexadecimal location 40, enter display H40.
    2. Separate each set of display requests from others by at least one blank. For example, if you want to display hexadecimal location 40 and the contents of register 5, enter display H40 G5.
  2. The defaults for the following DISPLAY operands are:
    Operand Default Before Rounding
    G 0-end
    G- 0-end
    G-5 0-G5
    G5- G5-end
    G5 G5
    T T0
    T- T0-end
    T-1000 T0-1000
    T1000- T1000-end
    T1000 T1000
    PSW Current
  3. When displaying a range of addresses or subchannels, the command operand must be followed by an address, a range, or by a hyphen (-), colon (:), or period (.). When displaying registers, the command operand can stand alone.
  4. If you enter a command line that contains an operand that is not valid, the DISPLAY command terminates when it encounters that operand. Any previous valid operands are processed before termination occurs.
  5. The DISPLAY command lets you display storage in the following formats:
    • Hexadecimal string/word segments
    • EBCDIC or ASCII translation
    • Hexadecimal word segments with EBCDIC translation
    • Instruction
    • Storage key
    Note: The EBCDIC translation is displayed only when the storage location contains the hexadecimal representation contained in a system translation table. This table is tailorable by the system programmer via the system configuration file. The IBM® supplied table supports translations for the hexadecimal representation of the digits 0 through 9, the uppercase and lowercase letters A through Z, and a number of special characters. In all other cases, a period (.) is displayed.

    If you enter multiple operands on a single command line to display storage and do not specify the format that you want the DISPLAY command processor to use, the last format type you explicitly enter on the command line defines the type of display you receive. That is, whenever you explicitly enter a display type, you implicitly define the default for subsequent operands of the current display function. If you do not enter any display format type on the command line, the system defaults are employed.

    For example, the command display 10 20 T40 80 G12 5 L60-100 displays the following, respectively:
    • Hexadecimal location 10 without EBCDIC translation
    • Hexadecimal location 20 without EBCDIC translation
    • Hexadecimal location 40 with EBCDIC translation
    • Hexadecimal location 80 with EBCDIC translation
    • The contents of general register 12
    • The contents of general register 5
    • Hexadecimal locations 60 through 100 without EBCDIC translation.
  6. Use the DISPLAY command to display the contents of various storage locations, registers, and control words. You can examine this information during program execution, and may be able to determine the cause of program errors.

    To do this, you would typically define a TRACE trap, using the TRACE command, that will stop program execution at a specified point. Once program execution suspends, your virtual machine enters the CP environment, and you can enter the DISPLAY command. Alternatively, you can process the DISPLAY command directly from TRACE using the TRACE command CMD option. For more information, see TRACE: Options.

  7. The DISPLAY storage command supports indirect addressing. Indirect addressing tells the command to use the contents of an address you specified instead of the address itself. This can help reduce the number of displays you issue and the tedious tracking of address pointers. You specify indirect addressing with an & (for 64-bit) or a % (for 31-bit).
    The following is an example of double indirection using the % for 31–bit addressing. First, the storage is shown using the usual DISPLAY without indirect addressing. Following that is the same storage displayed using indirect addressing with only one DISPLAY command (and without having to know that the information you want is at address 3F1AB40). The information displayed is a LNGBK control block for the system default language using a pointer from the CP nucleus SYSCM area. 
     D 3EF1030                                         
 R03EF1030  0000524C                            
                                                   
 D 524C                                            
 R0000524C  03F1AB40                           

                                                                      
 D T3F1AB40.80                                                        
 
     R03F1AB40  00000000 00000000 00000000 00000000 06 *................* 
 R03F1AB50 to 03F1AB5F suppressed line(s) same as above ....          
 R03F1AB60  00390000 00000000 C1D4C5D5 C7000000    *........AMENG...* 
 R03F1AB70  00000000 03F1A878 00000000 0041E000    *.....1y.........* 
 R03F1AB80  C8C3D7D4 C5E24040 00000000 00000000    *HCPMES  ........* 
 R03F1AB90  00000000 00000000 00000000 00000000    *................* 
 R03F1ABA0 to 03F1ABAF suppressed line(s) same as above ....          
 R03F1ABB0  4CD3D5C7 4C4C4C4C 80000070 00D5D3E3    *<LNG<<<<.....NLT* 
     D T3EF1030%%.80
 
     R03F1AB40  00000000 00000000 00000000 00000000 06 *................* 
 R03F1AB50 to 03F1AB5F suppressed line(s) same as above ....          
 R03F1AB60  00390000 00000000 C1D4C5D5 C7000000    *........AMENG...* 
 R03F1AB70  00000000 03F1A878 00000000 0041E000    *.....1y.........* 
 R03F1AB80  C8C3D7D4 C5E24040 00000000 00000000    *HCPMES  ........* 
 R03F1AB90  00000000 00000000 00000000 00000000    *................* 
 R03F1ABA0 to 03F1ABAF suppressed line(s) same as above ....          
 R03F1ABB0  4CD3D5C7 4C4C4C4C 80000070 00D5D3E3    *<LNG<<<<.....NLT*
  8. If the DISPLAY command processor is suppressing identical lines, it issues a response every time a segment boundary is crossed, rather than waiting for a nonidentical line.
  9. If you issue DISPLAY with the ASIT operand and specify the ASIT of a space owned by a user that has been relocated by the VMRELOCATE command prior to a subsequent reset clear function, the DISPLAY is rejected and error message HCPCDL6156E is issued. To avoid this situation, issue a command that initiates a reset clear function on the user on the relocation target system. Then obtain the new ASIT value by using the QUERY SPACES command or the ADRSPACE QUERY API from a program. Commands that result in a reset clear include:
    • SYSTEM CLEAR
    • IPL by NSS name
    • IPL by device with the CLear option
    • SET MACHine (to a different machine architecture)

Messages

(General for DISPLAY)

  • HCP003E Invalid option - {option|command contains extra option(s) starting with option}
  • HCP005E Invalid hexdata - hexdata
  • HCP009E Invalid range - range
  • HCP010E Invalid register - register
  • HCP026E Operand missing or invalid
  • HCP160E Hexloc hexloc exceeds storage
  • HCP164E Hexloc hexloc non-addressable storage
  • HCP260E {Command|command command} processing cannot complete due to errors.
  • HCP267E A subchannel number was not supplied or is invalid.
  • HCP410E CP ENTERED; PAGING ERROR
  • HCP422E The same option was specified twice.
  • HCP1001E An operand is missing for option.
  • HCP1003E {CP module name|rdev|ldev} {is|was} not found.
  • HCP1459E The virtual machine is placed in check-stop or system check-stop state due to a system malfunction with CPU nn.
  • HCP6150E An option has been specified that is not valid in {ESA/390|ESA/XC|z/Architecture®|z/XC} mode.
  • HCP6151E Storage {operand} is not addressable because of { a protection | an addressing | a segment translation | a page translation | a translation specification | an ASN translation | an AFX translation | an ASX translation | an ALET translation | an ALEN translation | an ALE sequence | an ASTE validity | an ASTE sequence } exception.
  • HCP6155E Storage is not addressable because of an invalid PSW.
  • HCP6156E {ASIT asit|Address space identifier spaceid} does not designate an address space to which you have the appropriate access.
  • HCP6525E Authorization request failed.
  • HCP6578E Invalid {access register|ASIT|address space identifier} - option