The same macro definition can be made available to more than one source program by placing the macro definition in the macro library. The macro library is a collection of macro definitions that can be used by all the assembler language programs in an installation. When a macro definition has been placed in the macro library, it can be called by coding its corresponding macro instruction in a source program. Macro definitions must be in a macro library with a member name that is the same as the macro name. The procedure for placing macro definitions in the macro library is described in the applicable utilities manual.

The DOS/VSE assembler requires library macro definitions to be placed in the macro library in a special edited format. High Level Assembler does not require this. Library macro definitions must be placed in the macro library in source statement format. If you wish to use edited macros in z/VSE you can provide a LIBRARY exit to read the edited macros and convert them into source statement format. A library exit is supplied with z/VSE and is described in z/VSE: Guide to System Functions.