An application package might have components and other large files that should be distributed to the Vespa nodes. Vespa can distribute these files efficiently to the nodes at the time of deploying an application (when doing vespa-deploy prepare).
Which files are distributed?
Distributed files are put in $VESPA_HOME/var/db/vespa/filedistribution on the nodes
When new components or files specified in config are distributed, the container gets a new file reference, waits for it to be available and switches to new config when all files are available.
vespa-status-filedistribution can be run to check if files have been distributed to all the hosts.