Method and means for making a dual volume level copy in a DASD storage subsystem subject to updating during the copy interval

Filing Information

• Patent Number: US5875479
• Application Number: US8779577
• Filing date: 01/07/1997
• Issue date: 02/23/1999
• Predicted expiration date: 01/07/2017

• U.S. Classifications: 711/162  · 711/112  ·
• International Classifications: G06F 1216 ·
• International Classifications: 711162;161;112;111 ·
• View document at: (opens new window):
  USPTO  ·  PAIR  ·  esp@cenet  ·  Patent Family
  * Related patent documents may or may not exist on these sites

Patent Family

Abstract

A volume-to-volume copy method on a DASD storage subsystem concurrent with host CPU application execution and referencing of data on a primary. In this method, updates to data made on a primary volume after the element was copied during a first pass will be deferred and copied only during a second pass rather than interrupting the first pass. This accumulation and deferral of updates to a second pass shortens the volume copy time and reduces application referencing delay.

Independent Claims | See all claims (10)

1. 1. A method for duplexing volumes on an external subsystem of tracked cyclic storage devices subject to host-originated updating, a volume being a unit of storage including the elements of one or more datasets or the like and accessible to a counterpart one of the storage devices, said duplexing to be used with any host-based copy functions such as concurrent copy or extended remote copy or subsystem-based copy functions such as dual copy or peer-to-peer remote copy, comprising the steps of:(a) forming a list structure defining copy status and copy order of the one or more data sets or descriptors in a first volume;(b) setting a first copy status value in the list structure to selected ones of the one or more datasets or descriptors in the first volume;(c) copying from the first to a second volume each of the one or more datasets or descriptors in the list structure having a copy status set to the first value in the defined copy order, and setting the copy status of each dataset or descriptor so copied to a second value; and(d) resetting the copy status in the list structure to the first value of any datasets or descriptors in the primary volume updated during the pendency of step (c) and already copied to the secondary volume; and repeating step (c) at least once.
2. 6. A system having a plurality of failure-independent tracked cyclic storage devices and at least a first control unit for establishing a write path to data stored on selective ones of the devices, said controller being responsive to an external command including parameters for duplexing a primary volume onto a secondary volume, a volume being a unit of storage accessible to a counterpart one of the storage devices, comprising at the first control unit:means responsive to the command parameters for building a list structure representative of the copy status of the contents of the primary volume and for setting the status of preselected contents thereof to a first value;means for copying in a first pass the preselected contents from the primary to the secondary volume in list structure order, for setting the status of the contents as they are copied to a second value, and for setting the status of those contents already copied to the secondary volume and again updated during the first pass to the first value; andmeans for copying in a second pass only those contents of the primary to the secondary volume in list structure order having a counterpart status set to the first value.
3. 10.10. An article of manufacture comprising a machine-readable memory having stored therein a plurality of processor-executable control program steps for duplexing volumes on an external subsystem of tracked cyclic storage devices subject to host-originated updating, a volume being a unit of storage including the elements of one or more datasets or the like and accessible to a counterpart one of the storage devices, said duplexing to be used with any host-based copy functions such as concurrent copy or extended remote copy or subsystem-based copy functions such as dual copy or peer-to-peer remote copy, said plurality of stored, processor-executable control program steps include:(a) a control program step for forming a list structure defining copy status and copy order of the one or more data sets or descriptors in a first volume;(b) a control program step for setting a first copy status value in the list structure to selected ones of the one or more datasets or descriptors in the first volume;(c) a control program step for copying from the first to a second volume each of the one or more datasets or descriptors in the list structure having a copy status set to the first value in the defined copy order, and setting the copy status to each copied dataset or descriptor to a second value; and(d) a control program step for resetting the copy status in the list structure to the first value of any datasets or descriptors in the primary volume updated during the pendency of step (c) and already copied to the secondary volume; and for repeating step (c) at least once.