I don't think DMA is an option in VMS land. Just a lock held for regular interrupt driven packet delivery. Been a while since I've dealt with it.

This provides an in-depth description of the VCI API which is used to write your own ethernet frame handler. Some descriptions of when IOLOCK8 is held.

https://rtk.mirrors.pdp-11.ru/_vax/openvms.org.ru/vci1.html#...