Living Witness

Directorial debut of Tim Russ, a.k.a. Tuvok, and the only Voyager episode directed by him.

Since when does Voyager have a backup of the Doctor's program?

Ever since the Doctor received his mobile holo-emitter in Future's End: Part II (1996) the Voyager crew has worried about losing him entirely, because he is downloaded into the device and its damage or loss would mean the program's loss. In other words, nothing remained of the Doctor in the computer or as a backup when he was using the emitter.

This lack of a backup was never directly explained, but it made sense. The Doctor's program was large, so much so that in The Swarm (1996) Voyager has to sacrifice its Jupiter Station diagnostic program in order to allow the Doctor to expand into the diagnostic's storage capacity and thus continue running every day and expanding his personality.

The size of the program means it could perhaps not be backed up (the fact it can still be downloaded into the tiny mobile emitter can be explained by the fact this device is from the 29th century).