EP0602822A2
Expired / Lapsed
EP
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Remote data duplexing
Assignee: International Business Machines Corp
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Filing: 1993-12-01
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Granted: —
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Expires: 2013-12-01
Abstract
Abstract A system for asynchronously duplexing direct access storage device (DASD) data in a plurality of DASD subsystems has the advantage of decoupling the data duplexing operation from the DASD write I/O operation. This ensures the write does not incur unnecessary wait states in the subsystem. By establishing a sequence checkpoint at which time a set of information packets are grouped together and processed as a single sequence unit, this decoupling and independent operation takes place. Through this independence, data copying to a secondary location can take place without affecting the performance of the subsystems and also not affecting the corresponding integrity of the data that is being updated.
Inventors
- 👤 William Frank Micka
- 👤 Claus William Mikkelsen
- 👤 Robert Wesley Shomler
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 10:25
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/16; G06F11/20; G06F11/2053; G06F11/2056; G06F11/2071; G06F11/2074; G06F11/2064; Y; Y10; Y10S; Y10S707/00; Y10S707/99931
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
163 words
A method of asynchronously duplexing DASD data content from a DASD subsystem (14) for use in a system for duplexing remote data, the system including a plurality of direct access storage device (DASD) subsystems (14), each subsystem including a plurality of information packet messages associated with a DASD data write operation , each of the information packet messages having a time value associated therewith, each of the information packet messages having a sequence number, the method comprising the steps of: establishing (202) a session with each of the plurality of subsystems; reading (204) the information packet messages from each of the DASD subsystems after a write operation to the subsystem; establishing a sequence checkpoint to group a plurality of information packet messages together as a single sequence unit; sending the sequence unit to a secondary location (18) for processing; obtaining DASD data associated with the information packet messages from each of the subsystems; and sending the DASD data to a secondary location (18).
Claim 2
Dependent Claim
45 words
A method as claimed in claim 1 in which the step of reading further comprises the step of setting (302) a time of day clock value for each subsystem that can be correlated with a clock time for the others of the plurality of subsystems.
Claim 3
Independent Claim
29 words
A method as claimed in any preceding claim in which each of the subsystems create and queue (304) an information packet message each time a write operation is processed.
Claim 4
Dependent Claim
83 words
A method as claimed in Claim 1 in which the step of establishing a sequence checkpoint further comprises the steps of: searching (206) for the latest time value of the information packet messages from each of the plurality of subsystems; establishing (208) the earliest of the latest time value information packet as a checkpoint; and grouping all information packets from the plurality of subsystems which have a time value that is earlier than the time value of the checkpoint into a sequence unit.
Claim 5
Dependent Claim
39 words
A method as claimed in Claim 4 which further comprises the steps of: querying a subsystem if there is no write operation received from the subsystem; and causing the subsystem to send the last sent information packet time value.
Claim 6
Dependent Claim
38 words
A method as claimed in Claim 4 which further comprises the steps of: querying a subsystem if there is no write operation received from the subsystem; and causing the subsystem to send at least one information packet message.
Claim 7
Dependent Claim
157 words
A global sequencer for asynchronously duplexing information packet messages from the DASD subsystems for use in a system for duplexing remote data, the system including a plurality of direct access storage device (DASD) subsystems (14), each subsystem including a plurality of information packets associated with a DASD data write operation, each of the information packets having a time value associated therewith, each of the information packets having a sequence number, the global sequencer comprising; means (106) for establishing a session with each of the plurality of subsystems; means (104) responsive to the session establishing means for reading the information packets from each of the DASD subsystems after a write operation to the subsystem; means responsive to the reading means for establishing a sequence checkpoint to group a plurality of information packets together as a single sequence unit; and means responsive to sequence checkpoint establishing means for sending the single sequence unit to a secondary location for processing.
Claim 8
Dependent Claim
43 words
A sequencer as claimed in Claim 7 in which the session establishing means comprises means for setting a time of day clock value for each subsystem that can be correlated with a clock time for the others of the plurality of the subsystems.
Claim 9
Dependent Claim
27 words
A sequencer as claimed in Claim 8 in which each of the subsystems create and queue an information packet message each time a write operation is processed.
Claim 10
Dependent Claim
93 words
A sequencer as claimed in Claim 7 in which the sequence checkpoint establishing means comprises: means for searching for a latest time value of the information packet messages from each of the plurality of subsystems; means responsive to the searching means for establishing the earliest of the latest time value information packets as a checkpoint; and means responsive to the time value establishing means for grouping all information packets from the plurality of subsystems which have a time value that is earlier than the time value of the checkpoint into a sequence unit.
Claim 11
Dependent Claim
45 words
A sequencer as claimed in Claim 10 which further comprises: means for querying a subsystem if there is no write operation received from the subsystem; and means responsive to the querying means for causing the subsystem to send the last sent information packet time value.
Claim 12
Dependent Claim
43 words
A sequencer as claimed in Claim 9 which further comprises: means for querying a subsystem if there is no write operation received from the subsystem; and means responsive to the querying means for causing subsystem to send at least one information packet message.
References Cited (Backward Citations)
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