The Disk output is directed to the device specified by a SYSPARM and that device is addressed via the esoteric it was defined as in the IODF.
To allocate a tape device for output of the DMS and ARCHIVE procs, specify the Sysparms . Refer to the Disk tech doc for MERGE Examples.
You can have as many pairs of DYNnUNIT and ARESUNIn specified in SYSPARMS as you have different devices. To avoid confusion, these Sysparms should be specified in the SYSPARMS member only, and not with the override DD in the JCL.
You must leave the DYNnUNIT and ARESUNIn pairs in your SYSPARMS member as long as you have that media type in the Disk Archives.