The Coda system for restoring backed-up volumes is less satisfactory than the backup system. In particular the documentation is rather incomplete and contains some mistakes. You need to experiment with restoring volumes to understand exactly what you need to do.
The program `merge' combines one full and one incremental dump file to create a single dump file for the volume to be restored. If you have create several incremental dumps, you need to run merge several times. There is no script to restore a volume; you must figure out the correct commands and arguments to use. This procedure creates a new read-only volume, which you need to mount somewhere.
If you wish to restore a whole volume from its backup, you need to create a new read-write volume, and manually to copy the files, mount points, and ACLs from the restored volume. The notes say that restoring the whole system after a crash is difficult; it is in fact a very tedious job.