Parameter Description for Callable Services

All the parameters of the APPC/MVS callable services are required positional parameters. When you invoke a service, you must specify all the parameters in the order listed. APPC/MVS checks all parameters for valid values, regardless of whether the parameters are used in call processing. Even though a language may allow parameters to be omitted, APPC/MVS services do not.

Some parameters do not require values and allow you to substitute zeros or a string of blanks for the parameter. For example, if you do not specify a symbolic destination on the Allocate call, you must set the Sym_dest_name parameter to eight blanks. The descriptions of the parameters identify those which can be replaced by blanks or zeros, and when to do so.

In the descriptions of services in this document, each parameter is described as supplied or returned.

Supplied means that you supply a value for the parameter in the call.

Returned means that the service returns a value in the named parameter when the call is finished (for example, return_code).

Each parameter is also described in terms of its data type, character set, and length.

Data type is either integer, character string, or structure.

Character set applies only to parameters whose values are character strings and governs the values allowed for that parameter. Possible character sets are:

No restriction
There is no restriction on the byte values contained in the character string.
Type A EBCDIC
The string may contain only uppercase alphabetics, numerics, and national characters (@, $, #), and must begin with an alphabetic or national character. Use of @, $, and # is discouraged because those characters display differently on different national code pages.
01134
The string may contain uppercase alphabetics or numerics, with no restriction on the first character.
00640
The string may contain upper- or lowercase alphabetics, numerics, or any of 19 special characters with no restriction on the first character. This set is consistent with the 00640 character set except that APPC/MVS does not allow blanks in 00640 character strings.

For more detailed information about the characters in each character set, see Character Sets.

Length depends on the data type of the parameter.

For an integer item, the length indicates the size of the field in bits or bytes.
For a character string parameter, the length value indicates the number of characters that may be contained in a character type parameter. The length may specify a single number or a minimum and maximum number.
For a structure parameter, the length value indicates the size of the structure in bytes, or a minimum and maximum size if the size of the structure is variable.