Patent ID: 7707186

Claim:
In a data processing system in which at least one active application interacts with at least one data set, a data set having a defined plurality of extents in a source logical device, each data set being characterized by metadata that provides a basis for correspondence between logical device and data request addresses, a method for migrating the defined plurality of data extents to a target logical device in a consistent fashion concurrently with interaction between any of the at least one application and the defined plurality of data sets throughout the migration, said method comprising the steps in sequence of: A) establishing a first status and operating mode by generating control data structures for each of the source and target logical devices that identify the locations of each of the at least one data set extent in the source logical device and corresponding locations in the target logical device and status information related to the status and operating mode for each extent, data set, and logical device to be migrated, B) thereafter establishing for each extent a second status and operating mode during which data in the extent is copied asynchronously from the at least one data set in the source logical device to the target logical device and concurrently with interactions between the at least one application with the at least one data set in the source logical device, C) thereafter establishing a third status and operating mode for each extent in the data set during which the data in the corresponding extents in the source and logical devices are brought into and thereafter maintained in synchronism whereupon the extents in the source and target logical devices operate as synchronous mirrors such that any subsequent request to change data from any of the at least one active application during the third status and operating mode changes the data in the source extent and the corresponding data in the target extent is synchronously updated, D) thereafter establishing, concurrently with the interaction between any application and the data in an extent undergoing migration, a fourth status and operating mode wherein the metadata for each extent in the defined plurality of data extents is updated whereby each data request to an extent from any of the at least one active application is recast to interact in a diverted state with the data only in the corresponding extent in the target logical device, said establishment of the fourth status and operating mode for the defined plurality of data extents requiring that all the extents in the defined plurality of data sets be shifted to the diverted state simultaneously, and E) establishing, after all the applications that were interacting with the data in each data set being migrated during the fourth status and operating mode, a fifth status and operating mode during which the migration is terminated, control data structures are removed and operating system catalogs are updated.