System Software Operations Guide, Volume 2: Commands

Systems operators and programmers can direct the MCP to perform particular actions through the use of Master Control Program (MCP) system commands. These commands have many functions, including display or change of system, program, or device status and initiation and control of various system utilities. This guide lists the system commands in alphabetical order and discusses the use and syntax of each command.

System commands can be entered in the following ways:

  • At an Operator Display Terminal (ODT) or Operator Control Station (OCS).
  • Through the programmatic ZIP and ZIPSPO facilities in the syntax of the different programming languages. Most programs can contain ZIP statements that pass system commands to the MCP.
  • Through programmatic SPOMESSAGE Branch Communicates (SPOM BCTs) that request information from the MCP.
  • Through a card reader or pseudo card reader.
  • Through the command capabilities provided with some programming tool packages, such as the Command and Edit (CANDE) system and the Programmer Productivity System (PROPS).
  • Through the Work Flow Language (WFL).
  • Through the Remote Job Entry (RJE) system, which enables communication between a remote site and a central system.
  • Through the BNA network architecture system, which enables communications between remote systems.

Keyboard Input Messages Versus MCP Control Instructions

There are two types of MCP system commands: keyboard input messages and MCP control instructions. Each of the commands described in this guide specifies whether it is a keyboard input message or an MCP control instruction.

Keyboard input messages have a wide range of functions, such as inquiry and system maintenance. For the most part, keyboard input messages are 2- or 4-character abbreviations, such as DD (Delete DLP) or TR (Time Reset).

The MCP control instructions generally affect a program in the mix by either initiating a program or providing special parameters for the execution of a program. These control instructions are mostly full-word commands, such as EXECUTE (Execute Library Program) or PERFORM (Schedule DMPALL).

The precise differences in how the two are entered are as follows:

  • The SPOMESSAGE BCT passes only keyboard input messages to the MCP, not MCP control instructions.
  • A keyboard input message entered from a card reader or in a programmatic ZIP must be prefaced by SPO.
  • When you enter commands through a ZIP statement within a program, the syntax among the different programming languages does vary, but MCP control instructions are usually preceded by ZIP, and keyboard input messages by ZIP SPO.
  • A keyboard input message entered through CANDE or a programmatic SPOMESSAGE BCT is displayed on the ODT as ”=⇒ SPO” followed by the text that was sent. An MCP control instruction entered through CANDE or RJE is displayed as ”=⇒” followed by the text you sent.
  • All MCP control instructions supplied through the keyboard can optionally be prefaced with the CC (Enter Control Instructions) command (for example, CC EXECUTE MYPROG).
  • If a system running MCP/VS relase 2.0 or later is communicating with a system running MCP/VS 1.0 through BNA, the CC is mandatory when using MCP control instructions after the AT (Initiate BNA Job Transfer) command, which initiates a BNA job transfer between a local host and a remote host.

Entering Commands through the ODT

System commands are entered at the top line of the ODT, and they can continue to subsequent lines.

To enter commands through the ODT, do the following:

  1. Position the ODT cursor at the top of the screen by pressing the CLEAR/HOME key, if necessary.
  2. Type the desired command.
  3. If the ODT is a T27, B 20, ET 1100, TD 830, or MT 983 device, you can transmit the command by pressing the transmit key. All data preceding the cursor will be transmitted to the MCP. For other devices, press the End-Of-Text (ETX) key, which places an ETX character on the screen and returns the cursor to the Home position. Then press the transmit key.

Optionally, the command can be terminated with a period (.) character prior to the ETX, in which case all text following the period is ignored. When the MCP acknowledges the command, the ODT is set in receive mode.

If you have multi-line input, put an ETX character at the end of the message, put the cursor at the beginning of the message, and then press the transmit key.

Note: Pressing the transmit key causes everything from the ODT cursor to the ETX character to be sent to the MCP. It is important, therefore, that the cursor be positioned at the beginning of the message before the transmit key is pressed and that no spurious ETX characters be on the screen.

If you make an error while typing in a command, press the CLEAR/HOME key and then retype the command.

If a command is entered incorrectly, the MCP returns the following message:


MCP Response to ODT Input

The MCP responds to ODT keyboard input in the following way:

A single-line response to an input request will be displayed on the second line of the screen (the remainder of the screen will not be cleared). For a multiple-line (or no-line) response, the second line of the screen will be cleared. A multiple-line response will be displayed following the header and any skip-lines.

System commands are indented one additional space when they are displayed on the ODT “messages” screen and in the ODT log listing to make it easier to identify input requests. However, this does not affect keyboard output messages returned to a SPOMESSAGE BCT.

The system message display is indented four spaces. The lines that have not previously appeared in a display will be highlighted, independently of system message displays on any other ODT terminal. It will therefore be possible to see at a glance which messages are new.

When input messages are entered from an ODT, they appear in a DQ (Display System Messages) command response and/or from the AD MSG display. All input messages are flagged with ”=⇒” to the left of the display line.

If the command requires the MCP to display multiple lines, all available lines except the communication interface area and lines reserved by the ODT SK option are used, and lines currently being displayed are overwritten or erased. See UNIT Record and the AD (Specify ODT Screen Parameters) command for a description of the ODT SK, HDR, and MSG options.

Replies that exceed one line remain on the screen for 30 seconds or until the system operator enters an ETX (or transmits blanks) for a new screen display, an ES (End Screen - ODT Only) command to end screen display, or another input request that would cause the current display to be overwritten or erased.

If the reply to the command requires more lines than are available on the ODT screen, the MCP uses all available lines except the communication interface area lines and the lines reserved by the ODT SK option. The MCP then displays “MORE DATA” in the communication interface area. No more data is written on the screen for 30 seconds or until the system operator enters an ETX, one or more blanks, ES, or another keyboard input request. If, after 30 seconds, the system operator has not performed any of these operations, the MCP displays a new screen containing the overflow data.

Entering Commands through a Programmatic ZIP or ZIPSPO

The commands sent with the ZIP or ZIPSPO facilities are acted on exactly as if they had been entered at the ODT. The ZIP and ZIPSPO facilities are invoked by constructs in the various programming languages, which are discussed in the various language manuals.

If a program under execution contains a ZIP or ZIPSPO statement or equivalent syntax in a programming language that performs communication with the MCP, the statement must refer to a data area within the program. The information in that data area must conform to the following rules:

  • Unless the first character of the command is a period, the data area is assumed to be 73 characters long. The text can be up to 72 characters long, followed by a period. If a period is not present, the MCP will insert one in the 73rd character position.
  • If the first character of the command is a period, the data area can be of any length, and the MCP will not insert a period. The end period must therefore be present in the program.
  • The hyphen (not enclosed in parentheses) cannot be used as a continuation character in a ZIP statement.
  • The program must be able to handle 4-digit mix numbers.

Note that MCPIX commands not supported by MCP/VS cannot be used in a ZIP statement.

Entering Commands through a ZIPSPO

The ZIPSPO function gives a user program the ability to pass control information to the MCP and to determine if any errors occurred during the processing. If there is an error, a response will be returned to the program.

The ZIPSPO response area is 82 characters long. The first two characters contain a numeric error code; the remainder contains the text.

If no errors are detected, the error code will contain “00” followed by a 4-character value containing the Run log number of the last job initiated by the ZIPSPO or “0000” if no jobs were initiated. The remaining 76 characters are undefined. If an error is detected, the first two characters are non-zero and the following 80 characters will be a


keyboard response terminated by ETX.

Entering Commands through a SPOMESSAGE BCT

The SPOMESSAGE BCT passes keyboard input messages to the MCP and requests that the response be returned to the requestor. The input message must be terminated by either a period (.) or an ETX character.

Note that you cannot enter MCP control instructions through a SPOMESSAGE BCT.

The length of the response buffer must be at least 80 characters and must not overlap the input area. The output buffer should be cleared before calling this BCT.

If you enter a command not valid through a SPOMESSAGE BCT, a message stating that the request is not allowed appears on the ODT.

See the V Series Program Interfaces Programming Reference Manual for more information.

Entering Commands through Punched Cards

If punched cards are used to communicate a command, the following rules apply:

  • The first column must contain an invalid character, known as the Punched Cards Control Character. This control character is a punch combination that does not represent any valid character. For example, multi-punched 1-2-3 is most commonly used. Invalid characters are not allowed in any other column. The first word following the invalid character must be a valid command. When a command is contained in a pseudo-card file, the first column must contain a question mark character (”?”, EBCDIC 6F).
  • Only columns 2 through 72 can contain commands; the MCP ignores information after column 72. Commands can start in any position between columns 2 through 72.
  • If the special character period (.) appears in a control record, other than as part of a file name in parentheses, such as (B974.1), all information following the period is ignored for control purposes. This enables comments to be present in control records.
  • The special character semicolon (;) must be used to designate the end of a series of commands if a new command is to start on the same punched card or if the MCP would not otherwise recognize the new control data. This is used primarily to enter control data such as CHARGE, PRIORITY, MEMORY, and so forth, to a system intrinsic such as DMPALL. The semicolon can be used on a ?SPO record to designate multiple commands (for example,
    ?SPO KA =; MEM + 20 PR 5


  • Commands can be contained on more than one record, except for the ?SPO commands, which must always be contained on a single record. The continuation character hyphen (-) can be used to continue information from one record to another. The hyphen must not be used to divide any word. Any information following the hyphen (on the same record) is ignored. The record on which the information is continued must not contain an invalid character in column 1.
  • All commands are described in Section 2 under headings that appear to indicate that each of them must consist of a separate record (a COMPILE record, a PRIORITY record, and so forth). However, if the text of a command is delimited by a semicolon, indicating the logical end of that command, it can then be followed by another command on the same record.
  • Any program name or file name that begins with a number or contains special characters must be enclosed in parentheses.
  • The MCP treats every program name and file identifier as if it had six characters, and shorter identifiers are assumed to have an appropriate number of trailing blanks. Consequently, any program name or file identifier that contains special characters or embedded blanks must be enclosed in parentheses. It is syntactically correct to enclose only the actual identifier within parentheses. For example, (X-X) and (X-X ) are both correct.

Entering Commands through CANDE, PROPS, or WFL

The Command And Edit (CANDE) system is a multi-user timesharing facility that provides several levels of system and file access control.

The Programmer's Productivity System (PROPS) is an interactive program development environment.

The Work Flow Language (WFL) is a Unisys language used for constructing jobs that compile and run programs on Unisys computer systems. WFL includes variables, expressions, and flow-of-control statements that offer a range of task control capabilities.

Entering Commands through RJE

The Remote Job Entry (RJE) system is a software package that permits commands to be sent from a remote site to a central system, and that enables output of data from the central system to be sent to remote peripherals.

Entering Commands through BNA

BNA (Burroughs Network Architecture) is a software system used to link Unisys computer systems together in a data communications network. The BNA network supports full data communications, distributed processing, and virtual station transfer, as well as remote command entry.

Command Details

The following comments apply generally to all the system commands:

  • Leading zeros are generally optional unless otherwise specified.
  • The words and numbers in a system command are separated by delimiting characters, which are either blank spaces, commas, or semicolons. A space is sufficient in most cases.
  • Any number of spaces may be placed between words without affecting the meaning. For example, the following are equivalent:
              COPY A,B TO TAPE
              COPY A , B TO TAPE
              KS =; MEM +10
              KS = ; MEM + 10
  • Parentheses must be used to enclose identifiers containing non-alphanumeric characters.
  • Up to 400 bytes of input text can be entered from an ODT. It is not possible for a word to wrap around from one line to the next because the terminal automatically inserts a CR/LF at the end of each line transmitted.
  • You cannot use a mix number of 0 or 1 in a system command, except for the DM (Dump and Continue) command, which allows 0 DM. Mix numbers 0 and 1 are reserved for the use of MCP/VS. If you do enter a mix number of 0 or 1, an error message will be displayed.

File Identifiers

A file identifier is the name contained in the directory for the referenced device, such as a tape, disk, or pack. A file identifier can be up to six printable characters long, but cannot be made up of all blanks or all zeros.

All library maintenance commands use an expanded method of identifying a file identifier. A file identifier can contain any combination of printable EBCDIC characters with the exception of left and right parentheses, period, comma, semicolon, hyphen, slash, and space; however, these characters (except the right parenthesis) can be used if they are enclosed in parentheses.

An equal sign not enclosed in parentheses, used in any position of a file identifier, indicates that any character is acceptable in that character position. An equal sign used in this fashion is also called a masking character.

A file identifier that contains masking characters is referred to as a file-group identifier. Trailing equal signs are assumed if the file identifier ends with an equal sign.

The following examples, as shown in Table 1-1, are specific file identifiers that would be syntactically equal to the file-group identifier.

A= A
All file identifiers starting with the letter A
A A Only the file identifier A
=A= AA
All file identifiers with an A in the second character position
All file identifiers with an A in the first character position and a F in the sixth.

An equal sign must not be separated by a blank space from the letters of a file-group identifier. A single equal sign normally causes all file identifiers to be specified. Exceptions are detailed under each applicable system command.

The file identifiers listed in Table 1-2 are reserved for use by the MCP and cannot be used for user-created disk files.

Reserved File
ADFL*W AD rule overflow file (* is a system number and can be 0 through 3)
CONFG* System Configuration File (* is a system number and can be 0 through 3)
DSKAVL Disk Available Table
DSKDIR Disk Directory
hlparm Halt/Load Parameters
MCPMCP Operating MCP Area
mstavl Master Disk Available Table
nLOG*w MCP Logs (System Option Dependent). (n denotes the type of log and can be M, R or S), (* is a system number and can be 0 through 3) (w denotes a rotating log file number and can be 0 through 9; 0 is the current log file and X is a reserved log file).
PCRXRF Pseudo Card Reader dictionary
pntp*t Program Name Table (* is a system number and can be 0 through 3)
SQARCY Disk SQUASH recovery file
USERFL System Access Control File
USRCOM System Access Control File
$*0001 MCP Memory Dump Area (* is a system number and can be 0 through 3

Special Characters

Table 1-3 lists the special characters that cannot be used in a file identifier except when enclosed in parenthesis.

Period (.) A period delimits an ODT message line or system command on one record.
Semicolon (;) A semicolon denotes another system command to immediately follow.
Comma (,) A comma delimits a file identifier
Hyphen (-) A hyphen indicates command continuation.
Equal (=) An equal sign indicates a masking (wildcard) character position.

Be careful when using file identifiers that begin with special characters that are also used by the MCP, such as the following:

  1. @ which identifies a printer backup file
  2. # which identifies a pseudo card deck
  3. * which identifies a punch backup file
  4. $ which identifies a dump file

Command Restrictions

The following restrictions apply to the various system commands:

  • The following commands are invalid from a programmatic ZIP or ZIPSPO:
          ALLOCATE         DISK             HL               QWIKPOOL
          ALTER            DISPLAY/WHATS    ID               QWKMEM
          BCL              DL               KX               SHOW
          BINARY           DLP              LABEL1           UNIT
          BO               DQ               LO               XA
          DATA/DATAB       EBCDIC           PACK
          DD               ED               PATCH
          DEBUG            ES               QD
  • The REMOVE === (remove all files) command cannot be issued using a programmatic ZIP since it requires a NULL mix.
  • The following commands are invalid from a SPOMESSAGE BCT
          AC               HL               PB               RY
          AD               ID               PC               SD
          AT               IL               PG               SI
          BO               KA               PM               SM
          BT               KP               PO               SN
          CV               KS               PP               SP
          DD               KX               PR               ST
          DL               LD               PS               SV
          DM               LH               QD               TL
          DP               LN               QT               TM
          DR               LO               RA               TR
          DS               MR               RM               UL
          ED               NET              RN               XA
          ES               NW               RP               XD
          ET               OF               RQ               XM
          FM               OK               RS               XP
          FP               OU               RW
          FR               PA               RX
  • The following commands are invalid through a Card Reader (?SPO commands):
          BO               ED               KX               XA
          BT               ES               LI
          DEBUG            ET               LO
          DQ               ID               QD
  • The following commands are invalid from a WFL handler:
          ADD              LOAD             PRM              UNLOAD
          CHECK            PRIORITY         PRP
          DUMP             PR               PRS
  • The following commands are invalid through Remote Job Entry (RJE):
          AC               ED               PR               SO
          AD               ES               PRIORITY         SP
          ADD              ET               PRM              SQ
          ALLOCATE         HL               PRP              SV
          ALTER            ID               PRS              TL
          AT               IR               QD               TM
          BT               KX               QWIKPOOL         TR
          CHECK            LABEL1           QWKMEM           UNIT
          CK               LD               RO               UNLOAD
          DB               LH               RP               UR
          DD               LN               RQ               XA
          DISK             LOAD             RW               XC
          DISPLAY/WHATS    NET              RX               XD
          DL               NW               RY               XM
          DLP              PACK             SD               XP
          DR               PATCH            SHOW
          DUMP             PG               SI
          DX               PO               SN
  • The DM command is valid for MCP mix number 0.

Access Level

A terminal can be restricted to permit input of only certain types of system commands. These restrictions can be set in the LEVEL parameter of the UNIT ODT record of the system configuration file, which declares the terminals that communicate with the MCP.

Table 1-4 shows the type and access level of each command.

Note that all commands permitted to lower-level ODTs are also permitted to ODTs with higher classifications. Except for level 8 or 9 ODTs, commands requiring a <mix no> can be used only if the <mix no> refers to a program originating from the station that also originated the command.

0 1 3 5 7 8
Inquiry Job
ssog2/commands.txt · Last modified: 2011/05/16 18:58 by scott
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