Characteristics of a Command Model

Syntax Model Command Language › Characteristics of a Command Model

Characteristics of a Command Model

Take a look at some of the CP commands that are documented in the IBM CP Command Reference. Notice that:

Most CP commands can have multiple formats
Different privilege classes of users have different operands available to them
Optional operands can appear in any order or in a specified order
Some commands have default operands
Operands can be mutually exclusive
Operands are sometimes preceded by a keyword descriptor
Operands are sometimes repeated.

To illustrate some of these characteristics, review the standard syntax for the IPL command in the next figure.


Ipl       {vaddr [cylno ] {CLear  }              }
          {      [nnnnnn] {NOCLear} [STOP] [ATTN]}[PARM p1 [p2..[p32]]]
 
           systemname

While reviewing the IPL command syntax, notice:

There are two command formats. You can IPL a vaddr or a systemname.
When you IPL a vaddr, you can also specify one or more optional operands. There are two groups of optional operands. The first group includes cylno, nnnnnnnn, CLear, NOCLear, STOP, and ATTN. Both groups include (PARM p1 [p2..p32].
Some operands have default values. For example, if you IPL a vaddr, then NOCLear is the default.
Some operands are mutually exclusive, meaning you can only use one of them. For example, CLear and NOCLear are mutually exclusive.
Notice how the PARM operand relates to p1. PARM is a keyword descriptor for p1, so that CA ACF2 for z/ VM does not confuse it with any other operand. When you specify PARM, you must also include at least one parameter (p1) following the keyword PARM. The parameters p2 through p32 are optional. In command model terminology, these parameters can occur 31 times.
Some operands have constant values. We show them in caps. They include CLear, NOCLear, STOP, ATTN, and PARM.
Operands that are constants do not have transposition routines. Other operands are variables. We show these in lower case. They include vaddr, systemname, cylno, nnnnnn, and p1...p32. Operands that are variables are always associated with a transposition routine.

The syntax model command language provides a relatively straightforward method for modelling a command. An example of how the IPL command is modelled follows:

Notes:    SMCL CLAUSES:

 1.       COMMAND IPL
             *
 2.             FORMAT CLASS=G
 3.               OPERAND vcuu,4,TRAN=VCUU
 4.               OPERAND GROUP=OPTIONS
 5.               OPERAND GROUP=PLIST
                FORMAT END
 
 6.             FORMAT CLASS=G
 7.               OPERAND systemname,8,TRAN=ANY
 5.               OPERAND GROUP=PLIST
                FORMAT END
 
 4.       OPTIONS GROUP TYPE=OPTIONAL
                    OPERAND LIST=((cylno,3,TRAN=HEX),     -
                                  (nnnnnn,6,TRAN=DECIMAL))
                    OPERAND LIST=((CLEAR,2),             -
                                  (NOCLEAR,4,TYPE=DEFAULT))
                    OPERAND STOP,4
                    OPERAND ATTN,4
                  GROUP END
 
 5.       PLIST   GROUP TYPE=KEYWORD
                    OPERAND PARM,4
                    OPERAND P1,8,TRAN=ANY
                    OPERAND P2,8,TRAN=ANY,OCCURS=31,OPTIONAL
                  GROUP END
 8.       COMMAND END

Most of the supplied models shown in this guide apply to VM/HPO Release 4.2 systems.

Notes on SMCL Clauses

This is the SMCL for the IPL command. It signifies the beginning of the IPL command.
This is the first format of the IPL command. All the operands for this command format are described in the boundaries of the FORMAT clause (you must describe all operands before the FORMAT END clause). There is also a second format allowed for IPL, but it is described in its own FORMAT clause (see Notes 6 and 7).
The first operand in the first format is vcuu that has a maximum length of four characters. Because there is no way to know what value vcuu is when you enter the command, CA ACF2 for z/ VM uses a transposition routine (TRAN=VCUU) when you enter the IPL command. This verifies that the value entered is a valid hexadecimal value.
The group called OPTIONS describes several optional operands.
```
OPTIONS GROUP TYPE=OPTIONAL
          OPERAND LIST=((cylno,3,TRAN=HEX),        -
                        (nnnnnn,6,TRAN=DECIMAL))
          OPERAND LIST=((CLEAR,2),                -
                        (NOCLEAR,4,TYPE=DEFAULT))
          OPERAND STOP,4
          OPERAND ATTN,4
        GROUP END
```
See how the CLEAR and NOCLEAR operands are described in the model. These are called mutually exclusive operands, meaning you can choose either CLEAR or NOCLEAR, but not both. The 2 following CLEAR and the 4 following NOCLEAR indicate the minimum length of these operands. NOCLEAR is identified as the default operand through a TYPE=DEFAULT verb. The GROUP END clause signals the end of this operand group.
There is another set of keyword operands that are described in a group called PLIST.
```
PLIST  GROUP TYPE=KEYWORD
         OPERAND PARM,4
         OPERAND P1,8,TRAN=ANY
         OPERAND P2,8,TRAN=ANY,OCCURS=31,OPTIONAL
       GROUP END
```
The first parm value (P1) means that you must enter at least one value whenever you specify the PARM keyword.

If you specify PARM with nothing following it, CA ACF2 for z/ VM stops looking at the command model and signals a syntax error.
The OCCURS=31 verb indicates that you can enter up to 31 parm values (p2,...,p32). However, the OPTIONAL verb says that p2, p3, are optional and you do not need to specify them. The GROUP END clause signals the end of this operand group.
This is the second format of the IPL command. All the operands for this command format are described in the boundaries of the FORMAT clause (all operands are described before the FORMAT END clause).
The first operand in the second format is systemname that has a maximum length of eight characters.

Because there is no way to know what value systemname is when you enter the command, a transposition routine (TRAN=ANY) is used when you enter the IPL command. This verifies that the length of systemname is one to eight characters. This FORMAT clause also references the GROUP clause labeled PLIST (see Note 5).
The COMMAND END statement signals the end of this command model.
The next section describes each syntax model command language clause and its verbs in detail.