A method of determining whether to use a repository to store data updates during a resynchronization, the method comprising the steps of: transferring writes to a primary storage to a secondary storage in a mirror copy relationship; establishing a logical copy of the secondary storage as of a point-in-time; storing writes to the secondary storage, received from the primary storage during a logical copy duration after the point-in-time, in a repository that comprises less storage space than the secondary storage; suspending the transferring of writes to the secondary storage, wherein during the suspension writes to the primary storage are indicated in an out-of-synch data structure; the method being characterised in further comprising the steps of: in response to ending the suspension of the transferring of writes from the primary storage to the secondary storage, determining whether available storage space in the repository is sufficient to store writes transferred from the primary storage, while transferring the writes from the out-of-synch data structure; using the repository to store data in the secondary storage as of the point-in-time that is to be updated by writes transferred from the primary storage following the ending of the suspension, in response to determining that the available storage space in the repository is sufficient to store writes transferred from the primary storage while transferring the writes indicated in the out-of-synch data structure; and using a third storage equal in size to the secondary storage to store data in the secondary storage updated after the suspension, in response to determining that the available storage space in the repository is not sufficient to store writes transferred from the primary storage while transferring the writes indicated in the out-of-synch data structure, wherein the third storage additionally stores data copied to the repository before the suspension of the writes. transferring writes to a primary storage to a secondary storage in a mirror copy relationship; establishing a logical copy of the secondary storage as of a point-in-time; storing writes to the secondary storage, received from the primary storage during a logical copy duration after the point-in-time, in a repository that comprises less storage space than the secondary storage; suspending the transferring of writes to the secondary storage, wherein during the suspension writes to the primary storage are indicated in an out-of-synch data structure; the method being characterised in further comprising the steps of: in response to ending the suspension of the transferring of writes from the primary storage to the secondary storage, determining whether available storage space in the repository is sufficient to store writes transferred from the primary storage, while transferring the writes from the out-of-synch data structure; using the repository to store data in the secondary storage as of the point-in-time that is to be updated by writes transferred from the primary storage following the ending of the suspension, in response to determining that the available storage space in the repository is sufficient to store writes transferred from the primary storage while transferring the writes indicated in the out-of-synch data structure; and using a third storage equal in size to the secondary storage to store data in the secondary storage updated after the suspension, in response to determining that the available storage space in the repository is not sufficient to store writes transferred from the primary storage while transferring the writes indicated in the out-of-synch data structure, wherein the third storage additionally stores data copied to the repository before the suspension of the writes. in response to ending the suspension of the transferring of writes from the primary storage to the secondary storage, determining whether available storage space in the repository is sufficient to store writes transferred from the primary storage, while transferring the writes from the out-of-synch data structure; using the repository to store data in the secondary storage as of the point-in-time that is to be updated by writes transferred from the primary storage following the ending of the suspension, in response to determining that the available storage space in the repository is sufficient to store writes transferred from the primary storage while transferring the writes indicated in the out-of-synch data structure; and using a third storage equal in size to the secondary storage to store data in the secondary storage updated after the suspension, in response to determining that the available storage space in the repository is not sufficient to store writes transferred from the primary storage while transferring the writes indicated in the out-of-synch data structure, wherein the third storage additionally stores data copied to the repository before the suspension of the writes.