A system and method for use in an automated data storage cartridge library defines cartridges for use with an external host computer ("open" cartridges), and cartridges for use only internal to the library ("closed" cartridges). Cartridges may be "virtualized" by storing data from them on disk or closed cartridges, and then "realized" by writing data to physical cartridges. Virtual cartridges may be logically exported from one library to another. When new cartridges are introduced to the library, they may be designated with one of multiple designations or uses.