The Default Parameter Block (DFPB)

The fourth word of the default parameter list must contain a pointer to the default parameter block (DFPB) built by the calling routine.

The default parameter block (DFPB) is shown in Table 1. You can use the IKJDFPB mapping macro, which is provided in SYS1.MACLIB, to map the DFPB.

Table 1. The default parameter block
Offset dec(Hex)	Number of bytes	Field name	Contents or meaning
0(0)	4	DFPBDSN	The high-order byte of this field (DFPBCODE) is the entry code indicating the option requested. Table 2 describes the options and their meanings. The remaining three bytes contain the address of the data set name buffer. Your Command Processor must build a data set name buffer that contains the length of the unqualified data set name in the first two bytes followed by the data set name that was entered by the terminal user. If the data set name is less than 44 bytes in length, it must be left justified and padded on the right with blanks.
4(4)	4	DFPBPSCB	The high-order byte of this field (DFPBCNTL) contains control codes that your Command Processor sets to indicate the functions requested. Code Meaning DFPBUID (X'20') The user ID is to be prefixed to the data set name. DFPBRET (X'04') Return a copy of the added qualifier. A copy of this qualifier is stored in the location pointed to by the DFPBQUAL field. DFPBADD (X'02') Add the qualifier supplied by the terminal user, which is pointed to by the DFPBQUAL field. DFPBMSG (X'01') Issue a message to the terminal user. The remaining three bytes contain the address of the protected step control block (PSCB). You can obtain this address from the Command Processor parameter list (CPPL) that the TMP passes to your Command Processor.
8(8)	4	DFPBQUAL	The high-order byte (DFPBLOCR) contains the LOCATE return code. The remaining three bytes contain the address of the default qualifier.
12(C)	4	DFPBCAT	The address of the user catalog.
16(10)	4	DFPBPSWD	The address of the password.

Your Command Processor must specify an entry code in the DFPBCODE field of the DFPB to specify the functions requested. Table 2 describes the entry codes.

Table 2. The default service routine entry codes
Entry code	Meaning	Functions performed by IKJEHDEF
X'00'	Use the qualifier provided by the caller.	Uses the qualifier in the DFPB that is provided by the caller.
X'04'	Find a qualifier. If there is more than one, prompt the terminal user to choose one.	Performs the following functions: Builds a list of possible qualifiers. Prompts the terminal user to choose one. Checks the terminal user's response against the list.
X'08'	Find a descriptive qualifier, but do not interrupt the terminal user.	Performs the following functions: Builds a list of possible qualifiers. Returns control to the caller with a return code indicating that more than one qualifier was found; therefore, prompting is necessary.
X'0C'	Either use the qualifier specified in the DFPB, find one from the system catalog, or use a new one submitted by the terminal user.	Does one of the following: If a qualifier is provided in the DFPB, IKJEHDEF uses it. If no qualifier is provided: Builds a list of possible qualifiers. Sends list to terminal. Prompts terminal user to choose one from the list or submit a new one.

Note: Entry codes X'80', X'84', X'88', and X'8C' are the same as X'00', X'04', X'08', and X'0C' respectively, except that a catalog name and a password are obtained from the DFPB when X'80', X'84', X'88', or X'8C' are specified. For entry codes X'00', X'04', X'08', and X'0C', the system catalog is searched.