Abstract: A method and apparatus for migrating one or more data sets each having one or more extents from one or more source logical devices to one or more target logical devices concurrently with interaction between the application and the data being migrated. A background operation copies each extent from the source logical device to the target logical device in a copy state. When a certain level of data has been copied, the extent is locked to assure synchronization of the data in the target logical device to the corresponding data in the source logical device. The status is changed to a mirrored state. When the extents for a data set in a source logical device or in a group of data sets have been mirrored, all the extents are changed to a diverted state. I/O requests to the diverted extents thereafter are intercepted and processed according to whether they access an extent that is in the copy, mirrored, or diverted state.

Abstract: The present invention is directed to a method of, and apparatus for, improving the efficiency of transferring data between a transmitting unit and a receiving unit in an end-to-end layer of a network which does not support full duplexed communication at the end-to-end layers. The method comprises the steps of determining a window size N, where N represents the number of frames which can be received by the receiving unit. The transmitting unit: sets a current window size equal to 2N minus one; accepting a frame of data for transmission; decrements the current window size; transmits the data if the current window size does not equal zero or, if the current window size equals zero, waits to receive a message from the receiving unit before transmitting the data; resets the current window size to the current window size plus N upon receipt of the message: and returns to the accepting data step if all data has not been sent.