The ddname list is a parameter list containing alternate ddnames for the data sets or volumes that you want the utility program to use. If you are using the standard ddnames for your data sets, you do not need to code a ddname list, unless you code a page header parameter.

An example of a case where you might want to use alternate DD names is when your program is calling various programs that use the same DD name for different data sets. Another example is when a program dynamically allocates a data set and writes utility control statements to it before calling a utility.

The ddname list should begin on a halfword boundary. The two high-order bytes must contain a count of the number of bytes in the remainder of the list. Each ddname must take up 8 bytes. If a ddname is shorter than 8 bytes, it must be left aligned and padded with blanks. If you code binary zeros for a ddname, or if you omit a ddname by shortening the ddname list, the standard ddname is assumed. You cannot omit a ddname from the middle of the ddname list without replacing it with binary zeros.

The general structure of the ddname parameter list (DDNMELST) is:

For example, to start IEBCOPY using nonstandard ddnames, you could code:

          LINK  EP=IEBCOPY,PARAM=(OPTLIST,DDNMELST),VL=1
          .
          .
          .
OPTLIST   DC  H'0'
DDNMELST  DC  AL2(L'DDNMEND)
DDNMPARM  DC  7XL8'0'
          DC  CL8'INPDS   '
          DC  CL8'OUTPDS  '
DDNMEND   EQU DDNMPARM,*-DDNMPARM
 

In this example, IEBCOPY is told to use INPDS as the input data set and OUTPDS as the output data set.

To start utilities such as IEBCOPY with multiple input or output data sets, it is necessary to pass a ddname list to the utility with alternative ddnames for SYSUT1 and SYSUT2. The utility control statements will be sufficient to identify the other ddnames that you require.

You do not need to code a ddname parameter list when you are invoking the IEH system utilities. The ddnames for these utilities define devices rather than data sets, and the utility control statements used by these utilities are sufficient for identifying the appropriate devices. The IEH utilities only use the entries for SYSIN and SYSPRINT from the ddname list.