Alas, the LINKER documentation (https://www.itec.suny.edu/scsys/vms/ovmsdoc073/v73/4548/4548...) I can find only includes a description of the "object language" for VAX (https://www.itec.suny.edu/scsys/vms/ovmsdoc073/v73/4548/4548...) and Alpha (https://www.itec.suny.edu/scsys/vms/ovmsdoc073/v73/4548/4548...). It does say that Itanium VMS used ELF format executables. So I think it's still an open question as to whether VAX/VMS or Alpha/VMS executable file format ever had documentation.

How did ELF format files play in VMS' idea of process-as-elaborate-address-sapce, where running a command involved reading or mapping in an executable, and then jumping to the entry point? Or did I64 VMS abandon the unusual VMS process model?