Patent ID: 8725691

Claim:
A method for dynamically changing the size of a LUN in a replication based environment, the replication based environment having a splitter, a production site and a replication site, the production site having a production LUN (Logical Unit Number), the replication site having a journal and a replication LUN, the method comprising: changing the size of the production LUN based on a request to change the size of the production LUN on the production site; determining on the replication site that the production LUN has changed size; determining whether it is possible to change the size of the replication LUN; wherein the determination of whether it is possible to change the replication LUN is negative when the size of the changed production LUN is smaller than the size of any corresponding point in time enabled by the replication based environment for the replication LUN; based on a negative determination and in response to a request for the replication LUN, pausing replication and based on a positive determination, changing or faking the size of the replication LUN; determining if there are applications replicated that are dependent on the size of the production LUN; based a positive determination, performing application pre-LUN increase activity; and performing, based on the positive determination, post-LUN increase activity; scanning the journal to determine the maximum size of the replication LUN in the journal; determining if the maximum size of the replication LUN in the journal is less than size of the replication LUN; and based on a positive determination, reducing the size of the replication LUN.