A storage system comprises a data set storage region or storing a data set containing data and update data for managing this data, and a control section. The data set storage region is divided into a plurality of storage regions including a first storage region and a second storage region. The control section generates a first data set containing first data and first update data which is update data for same, stores at least the first data of this first data set in the first storage region, generates a second data set containing second data and second update data which is update data for same, and stores at least the second data of this second data set in the second storage region, which is separate from the first storage region.

Database replication systems replicate blocks of transaction steps or operations with synchronous replication, and perform dual writes with queuing and blocking of transactions. Tokens are used to prepare a target database for replication from a source database and to confirm the preparation. Database replication systems switch between a synchronous replication mode and an asynchronous replication mode, and then back to a synchronous replication mode, based on detection of selected events.

A first storage unit system (104a) and a second storage unit system (104b) are connected together via a third storage unit system (104c). When executing a remote copy process, the first storage unit system responds to a write request received from a computer (102a) to transmit to the third storage unit system a journal having write data and address information indicative of a storage position at which the write data is written and requests the third storage unit system to write the journal. The second storage unit system receives control information (107a) issued by the first storage unit system and including the storage position of the journal and on the basis of the control information, reads the journal from the third storage unit system. Then, the second storage unit system follows address information contained in the journal to write the write date contained in the journal to a disk (210b) inside the second storage unit system.

A data processing system (50) includes a first storage system (10) including a first host (100A) and a first storage subsystem (200A). The first host has access to a first copy manager that is operable to manage a data replication operation. A second storage system (20) includes a second host (100B) and a second storage subsystem (200B). The second host has access to a second copy manager that is operable to manage a data replication operation. A first communication link (48) is coupled to the first storage system (10) and the second storage system (20) to exchange management information between the first and second storage systems in order to manage the data replication operation. A data transfer path (68) is configured to transfer data stored in the first storage subsystem (200A) to the second storage subsystem (200B) and replicate the data of the first storage subsystem (200A) in the second storage subsystem (200B). The data transfer path (68) is different from the first communication link (48).

Database replication systems replicate blocks of transaction steps or operations with synchronous replication, and perform dual writes with queuing and blocking of transactions. Tokens are used to prepare a target database for replication from a source database and to confirm the preparation. Database replication systems switch between a synchronous replication mode and an asynchronous replication mode, and then back to a synchronous replication mode, based on detection of selected events.

A primary computer system has a database, application programs that modify the local database, and a transaction manager that stores audit records in a local image trail reflecting those application program modifications to the local database. In a remote backup system, a Receiver process receives audit records from the primary system. The audit records include audit update and audit backout records indicating database updates and database backouts generated by transactions executing on the primary system. The Receiver stores the audit update and audit backout records in one or more image trails. For each image trail there is an Updater process that applies to a backup database volume the database updates and backouts indicated by the audit update and audit backout records in the image trail. The remote backup system periodically executes a file purge procedure, which identifies the oldest transaction table from among the transaction tables in the last image trail file accessed for each of the image trails. Then, for each image trail, the file purge procedure accesses the image trial files in a predefined chronological order and for each accessed image trail file it compares a first set of newest transaction identifiers in the file's transaction table with a second set of oldest transaction identifiers in the identified oldest transaction table. The procedure purges the accessed image trail file only when all of the transaction identifiers in the first set are older than corresponding transaction identifiers in the second set.