Parameter entries

Data is passed as parameter entries in a key, length, and data format. Figure 1 shows that Register 1 points to a list of addresses. Each address in the list points to a parameter entry.

The three parameter entry fields (key, length, and data) are described below:

Key

The key field is one fullword that contains a hexadecimal value. Table 1 shows the keys that have been defined for communication between the exit and the invoking program. Any other values are reserved and must not be used.

Table 1. Definition of keys for standard exit parameter list
KEY	Description
X'00'	No data is passed in this parameter entry.
X'01'	The data field contains the actual data for the parameter entry.
X'02'	The data field contains the address of the actual data for the parameter entry.
X'03'	This is a special key that only certain standard-format exits support. The exit requests that the function or command processor that invoked the exit routine use the exit reason code as the function's or command processor's return code. A key of X'03' is valid only for the exit reason code parameter entry (parameter entry 7). For more information, see Exit reason code.
X'04'	This is a special key that only certain standard-format exits support. The field is validated. This key indicates that the field contains valid data. When this key is set, the field is locked and cannot be altered.

Length

The length field is one fullword that contains the length of the data, in hexadecimal. For a key of X'01', the length is the length of the data in the data field. For a key of X'02', the length is the length of the data that the address in the data field points to.

The length field cannot be X'00'. If no data is passed in a parameter entry (key of X'00'), the length field must contain X'04'. If you use a key of X'03', the length field must also contain X'04'.

Data

The data field contains either the address of the data, the actual data, or a value of X'00'.

The value in the data field depends on the value in the key field. The following shows the relationship between the key and the value in the data field:

  Key         Data Field

  X'00'          X'00'
  X'01'          Actual data
  X'02'          Address of the data
  X'03'          Exit reason code
  X'04'          Field is validated

Figure 1 shows the values of the parameter entries that the first exit for a function or command processor receives. The first exit is usually the "initialization" exit for the function or command. The individual descriptions of each exit in this document describe any exceptions to the standard exit parameter list.

If information about a particular parameter is unavailable to a function or command processor, the function or command processor passes the following for the parameter entry:

Key: X'00'
Length: X'04'
Data: X'00'

An exit can change only the following parameter entries in the standard exit parameter list:

New command buffer.
Exit-to-exit communication word.

Depending on the individual exit, the exit may be able to change exit-dependent data that it receives. The individual descriptions of the exits in this document describe any exit-dependent data and whether the exit can change the parameter entries for this data. If the exit changes any of the other parameter entries, unpredictable results can occur.

If an exit changes the new command buffer, the exit-to-exit communication word, or any exit-dependent data, the function or command processor passes the changes to the next exit it invokes.

The following topics describe each of the standard parameter entries and the exit-dependent data.