Disk File Optimizer (DFO) for OpenVMS is a layered software product which reduces both file fragmentation and free space fragmentation and optimizes file placement on disk media. This results in better application performance, better backup performance, and more efficient disk utilization. DFO operates in two modes. In “Defrag PLUS” mode, RMS is used as a database of scheduling information, and defragmentation jobs can be scheduled using a wide variety of scheduling criteria. In nor- mal “Defrag” mode, defragmentation jobs are run when requested by the user. The user or system manager can specify which of these two modes should be used when the product is installed.