External dummy sections
An external dummy section is a reference control section that you can use to describe a communication area between two or more object modules that are link-edited together. The assembler generates an external dummy section when you define a Q-type address constant that contains the name of a reference control section specified in a DXD or DSECT instruction.
z/VSE® External dummy sections are only supported by VSE/ESA Version 2 Release 2 or later.