Method and apparatus for cascading data through redundant data storage units

A data network comprising:

• A) a production site with a host and an associated production site storage facility,
• B) a remote site with an associated remote site storage facility,
• C) a storage facility for interconnecting the production site and the remote site wherein the host can issue a plurality of cascade commands,
• D) a first data store for connection to the production facility for receiving data therefrom on a track-by-track basis,
• E) a second data store,
• F) first and second track status tables for identifying each track in said first data store that the production site changes,
• G) first operating means for establishing a first operating mode in response to a first cascade command during which said second data store receives data from said first data store according to the changes recorded in said first track status table,
• H) second operating means for establishing a second operating mode in response to a second cascade command for copying data from said second data store to the remote storage facility according to the changes transferred from said second track status table to a third track status table at the time the second mode is established.

A method for transferring data between a first facility in a network for altering data and a second facility in a network for receiving data including the steps of:

• A) establishing a first data store for receiving the altered data in the first facility,
• B) establishing a second data store,
• C) recording the identification of changes in the first data store produced by the facility for altering data in first and second locations,
• D) establishing a first operating mode during which the second data store receives data from the first data store according to the identified changes in the first locations,
• E) establishing a second operating mode for copying data from the second data store to the second facility according to the changes in the second locations identified at the time the second operating mode is established.

A method for transferring data between a production site with a host and an associated production site storage facility and a remote site with an associated remote site storage facility, wherein the host can issue a plurality of cascade commands, said method comprising the steps of:

• A) establishing a first data store for receiving data from the production facility on a track-by-track basis,
• B) establishing a second data store,
• C) defining a first and second track status tables for identifying each track in the first data store that the production site changes and a third track status table that identifies changes in the second data store,
• D) establishing a first operating mode in response to a first cascade command during which the second data store receives data from the first data store according to the changes recorded in the first track status tables,
• E) establishing a second operating mode in response to a second cascade command for copying data from the second data store to the remote storage facility according to the changes transferred to the third track status from the second track status table at the time the second mode is established.