With Nero Burning ROM you can compile and burn all types of files and folders to multiple discs. The DiscSpan (UDF) compilation type is useful when the data to be burned is too large to fit on a single disc or when a single fit exceeds the capacity of a disc. Nero Burning ROM splits such files automatically and distributes them dynamically among several discs.
The number of discs to be used is shown in the compilation screen and you can switch the disc type here. However, during the burn process you are allowed to alternate the disc types (CD, DVD, Blu-ray Disc) regardless of which disc type you chose at the beginning.
The restore tool Nero DiscMerge and a file catalog is burned on the last disc of the set by Nero Burning ROM. With this tool the split files can be merged together and copied to the hard drive. Files that are not split can of course be accessed without the help of Nero DiscMerge.  

Nero DiscSpan (UDF) Compilation and Nero DiscMerge Tool