Patent ID: 7788231

Claim:
A method processed by a computer system, comprising: maintaining a copy relationship associating a source storage and target storage pair, wherein writes received at the source storage are transferred to the target storage; calculating a receive signal interval as a function of a consistency group minimum freeze timeout time for copy managers residing in a plurality of control units less a freeze command runtime for a freeze operation to be implemented at the control units; sending out a signal at a higher frequency than the computed receive signal interval to the copy managers to ensure that the control units initiate freeze operations before other control units thaw and begin allowing write operations; determining whether the signal has been received from a consistency manager managing data consistency across multiple source storage and target storage pairs maintained by different of the control units within the receive signal interval; initiating the freeze operation to cease receiving writes at the source storage from an application in response to determining that the signal has not been received within the receive signal interval; and initiating a thaw operation to continue receiving writes submitted by the application at the source storage without transferring the writes from the application to the target storage after a lapse of a freeze timeout following the freeze operation to maintain data consistency at the target storages of the source and target storage pairs.