An external sort has been impplemented and analyzed for a shared disk MPP computer system. IN this implentation, we haave considered many real world constraints. Decision support functionality in database systems. for instance, often rewuires that external softin gbe done in place on disk, support variable length records, and be restarable from any point of intteruption with no loss of data. THese three constraints, along with the more standard rewuirements of speed and stabililty, affect the choice and implementation of the sample sort algorithm described here meets these requirements. Although written using high level file processing directives, the implementation sorts a 10 GB file in 1.5 hours on a 64 processor connection machine CM-5 with a data vault disk system