Releasing a data set at a source device in connection with migrating data from the source device to a target device includes mapping application address space to address space containing metadata for the target device and providing additional local metadata therefor, replacing within the application the address of metadata for the source device with the address of metadata for the target device, setting a diversion flag that is part of the additional local metadata, where the diversion flag indicates a remapping of extent, and closing and unallocating the data set at the source device. Releasing a data set at a source device in connection with migrating data from the source device to a target device may also include determining if an application uses standard I/O operations. The metadata may include UCB data.