Method of maintaining task sequence within a task domain across error recovery

Abstract

Tracks of data or other data units are copied from a primary storage system to a secondary storage system. For multiple-track or multiple-data unit transfers, a group of tracks or data units which are sequentially related are transferred. A respective task is defined at the primary storage system for monitoring a progress of the transfer of each of the respective data units in a group. A state is maintained for monitoring a progress of the transfer of the group responsive to the progress of each of the tasks. A normal state is selected when there are no failed tasks. A recovery state is selected when there is a failure, and the status of the remaining tasks is being ascertained. A retry state is selected following the recovery state to retry the failed tasks. A failed state indicates an unrecoverable failure.

1 . A primary storage system, comprising:
 a memory for storing software instructions; and   a control associated with the memory for executing the software instructions for:   initiating transfer of at least one group of data units from a primary storage system to a secondary storage system, said group of data units having a plurality of data units that are to be transferred;   defining a respective task for monitoring a progress of the transfer of each of the respective data units; and   maintaining a plurality of states for monitoring a progress of the transfer of said plurality of data units in the at least one group; said plurality of states comprising at least a normal state indicating that a data unit in the plurality of data units is ready to be transformed, a recovery state to which a task associated with a data unit transitions if the data unit had a recoverable failure but is not yet ready to retry, a retry state to which the task associated with a data unit transitions when status of all other data units in the plurality of data units is ascertained, and a failed state to which the task associated with a data unit transitions if the data unit had an unrecoverable failure;   wherein the states allow for error recovery of sending multiple data units.   wherein each of the units of data comprises a track of data;   the transfer of at least one group comprises a multi-track transfer;   wherein the transfer of a plurality of groups of data units from the primary storage system to the secondary storage system is initiated;   a respective task is defined for monitoring a process of the transfer of each of the respective data units in the plurality of groups;   a state is maintained for monitoring a process of the transfer of each of the groups;   for each of the groups, the state thereof is responsive to the process of each of the tasks thereof; and   maintaining data associating each of the tasks with its associated group.   
   
   
       2 . A program storage device, tangibly embodying a program of instructions executable by a primary storage system to perform a method for copying data, the method comprising:
 initiating transfer of at least one group of data units from a primary storage system to a secondary storage system, said group of data units having a plurality of data units that are to be transferred;   defining a respective task for monitoring a progress of the transfer of each of the respective data units; and   maintaining a plurality of states for monitoring a progress of the transfer of said plurality of data units in the at least one group, said plurality of states comprising at least a normal state indicating that a data unit in the plurality of data units is ready to be transmitted, a recovery state to which a task associated with a data unit transitions if the data unit had a recoverable failure but is not yet ready to retry, a retry state to which the task associated with a data unit transitions when status of all other data units in the plurality of data units is ascertained, and a failed state to which the task associated with a data unit transitions if the data unit had an unrecoverable failure;   wherein the states allow for error recovery of sending multiple data units.   wherein each of the units of data comprises a track of data;   the transfer of at least one group comprises a multi-track transfer;   wherein the transfer of a plurality of groups of data units from the primary storage system to the secondary storage system is initiated;   a respective task is defined for monitoring a process of the transfer of each of the respective data units in the plurality of groups;   a state is maintained for monitoring a process of the transfer of each of the groups;   for each of the groups, the state thereof is responsive to the process of each of the tasks thereof; and   maintaining data associating each of the tasks with its associated group.