Tom, in VMS and OpenVMS land back in Ye Olde Days we had what was called "Standalone BACKUP" on the VAX computers and that facility could be configured to boot from a variety of devices including an alternate disk, a CD, over the network and from some/most tape models. You could, with care, build a bootable tape and then put a BACKUP saveset on it so you had a self-contained bootable TAPE image from which you could boot and restore. A bootable image was built using SYS$UPDATE:STABACKIT.COM and it would properly configure and build that image directly on most of the media I listed above (excluding CD mainly but that speaks to other limitations).
When the Alpha was introduced decisions were made to limit the variety of solutions available for a bootable "Standalone BACKUP." The main solution on Alpha became booting from the O/S distribution CD and you could select from the menu an option to execute DCL commands. With that solution you had a very limited set of the DCL commands that would be mandatory for the regular needs of performing an "offline" BACKUP of most disks. This facility has been improved and enhanced so you can usually perform this "offline" BACKUP of most directly- and SAN-connected devices. Again, because many VMS people have long memories or well-established procedures cast in concrete, you can build an alternate bootable device using good ole SYS$UPDATE:STABACKIT.COM. The devices from which you can boot IS much more limited and you're essentially building, again, a very limited bootable OpenVMS system disk on an alternate drive but there isn't a way to build a bootable tape or directly burn your own bootable CD.
Integrity machines can also use the same command procedure, SYS$UPDATE:STABACKIT.COM and it will build a similar limited bootable OpenVMS system disk on an alternate device AND I'm pretty sure it'll link to other command procedures to create a "procedure" on the system's EFI boot area with pointers to the device you just built.
Another option? If you have setup a system as an Infoserver (using the Infoserver software available for OpenVMS) and have a bootable disk (a different one for each architecture of course) you can boot over the network from those devices instead of trying to build and boot from a device connected to the host you're backing up.
I know that isn't a fully direct answer to your question because, on Integrity/Itanium or Alpha, you can't really build a bootable TAPE backup. You would need to use the distribution DVD, like using the distro CD on Alpha, boot from the DVD and use the DCL commands options from the menu, check that your disk and tape are both available and then save to tape. Then in case you need to recover from a hard failure you boot from the DVD again and restore from the tape you made. From my experience you always want to have some form of BACKUP made like this in case you have a major failure but the main concern will always be taking the downtime necessary to spin the tapes. But if you don't have them you're stuck reinventing the wheel from an unfinished rock, so to speak.
