Method, system, and article of manufacture for creating a consistent copy

Abstract

Disclosed is a system, method, and article of manufacture for maintaining consistent copies of data between a primary site and a secondary site. One or more backup components receive backup messages from the primary site describing transactions. Transactions received from the primary site at the backup components are referred to as 'inbound transactions.' The backup components associate these inbound transactions with an identifier such that all transactions associated with a certain identifier comprise all of the activity on the consistency group for a certain period of time. The backup captain periodically notifies the backup components to pause (i.e., stop receiving inbound transactions temporarily), and once all backup components indicate that they have paused, the backup components are notified to resume receiving transactions and associate the newly received transactions with a new identifier. At the same time, the backup components are sending transactions to the secondary storage devices. Transactions sent from caches at the backup components to the secondary site are referred to as 'outbound transactions.' The backup components send all transactions from the current outbound consistent transactions set, temporarily stop sending outbound transactions, and notify the backup captain that they have completed sending the current outbound consistent transactions set. When all backup components have completed sending the current outbound consistent transactions set, the backup captain causes consistent copies to be made at secondary storage and notifies the backup components to send the next outbound consistent transactions set.