EP0600457A2
Expired / Lapsed
EP
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Distributed data processing system with replication of data across the system
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 Distributed data processing systems with replication of data across the system are required to provide data access and availability performance approaching that of a stand-alone system with its own data, but reductions in network traffic gained by replication must be balanced against the additional network traffic required to update multiple copies of the data. Apparatus and a method of operating a distributed data processing system is provided in which a currency period is associated with each copy of a data object and the data object is assumed to be valid during the currency period. The apparatus has means for checking (500) whether the currency period has expired and means for updating (570, 580) the copies. A validity indicator is set on determination of expiry of the currency period and when updates are applied to the primary copy, and is checked to determine validity of a copy. <IMAGE>
Inventors
- 👤 Geoffrey Sharman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 07:46
CPC Classifications
G; G06; G06F; G06F16/00; G06F16/20; G06F16/23; G06F16/2308; G06F16/2315; G06F16/2322; G06F16/27
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
97 words
A method of distributed data processing comprising storing at one or more remote data processors (200, 250) a replicated secondary copy (310) of a primary data record stored at a first data processor (100); propagating (420, 570) updates of said primary copy to the remote data processors (200, 250); storing at each of the remote data processors (200, 250) a currency expiry time (320) associated with each secondary copy stored at that data processor; and, in response to a request for data access at that data processor, checking (510) whether the currency expiry time (320) has passed.
Claim 2
Dependent Claim
64 words
A method of distributed data processing accordingly to Claim 1 including setting (460, 590) a validity indicator (330) when an update is applied to the primary copy during the currency period and, in response to a request for data access at a remote data processor, checking (500) the indicator (330) to determine whether the secondary copy held by said remote data processor is valid.
Claim 3
Dependent Claim
36 words
A method of distributed data processing according to Claim 1 or Claim 2 including requesting (530) an update of a secondary copy on determination of its invalidity or of the passing of its currency expiry time.
Claim 4
Independent Claim
56 words
A method of distributed data processing according to any one of Claims 1 to 3 including determining (400) which data records of a primary copy have been updated since the last update was propagated to the remote data processors holding secondary copies, and propagating (420) copies of said updated data records to the remote data processors.
Claim 5
Independent Claim
56 words
A method of distributed data processing accordingly to any one of the preceding claims, wherein updated copies of a data record are propagated (570) to a remote data processor only on request from said remote data processor (200) for access to said primary copy, said updated copies then being stored at the remote data processor (200).
Claim 6
Independent Claim
45 words
A method of distributed data processing accordingly to any one of the preceding claims including the step of logically partitioning the primary copy into non-overlapping parts to enable distributing the primary copy such that different data processors hold the primary copy for said different parts.
Claim 7
Dependent Claim
82 words
Distributed data processing apparatus comprising a first data processor (100) having means for storing a primary copy of a data record (310); at least one remote data processor (200) having means for storing secondary copies of all or part of the primary copy, means for storing a currency expiry time associated with each secondary copy, and means for checking whether the currency expiry time has passed; and means for propagating (420, 570) to the secondary copies updates applied to the primary copy.
Claim 8
Dependent Claim
55 words
Distributed data processing apparatus according to Claim 7 having means for setting a validity indicator (330) when an update is applied to the primary copy and means for checking (500) the indicator (330) in response to a request for data access at a remote data processor (200), thereby to determine the validity of the copy.
Claim 9
Dependent Claim
36 words
Distributed data processing apparatus according to Claim 7 or Claim 8 including means for requesting (530) an update of a secondary copy on determination of its invalidity or of the passing of its currency expiry time.
Claim 10
Dependent Claim
56 words
Distributed data processing apparatus according to any one of Claims 7 to 9 having means for determining (400) which data records of a primary copy have been updated since the last update was propagated to the remote data processors holding secondary copies, and means for propagating copies of said updated data records to the remote processors.
Claim 11
Dependent Claim
57 words
Distributed data processing apparatus according to any one of Claims 7 to 10 wherein updated copies of a data record are propagated (570) to a remote processor (200) only on request from said remote data processor (200) for access to said primary copy and wherein the remote data processor (200 has means for storing said updated copies.
Claim 12
Dependent Claim
43 words
Distributed data processing apparatus according to any one of Claims 7 to 11 wherein the primary data record is logically partitioned such that it may be distributed for different processors to hold the primary copy of different parts of the primary data record.
Claim 13
Dependent Claim
21 words
Distributed data processing apparatus according to any one of Claims 7 to 12 including means for setting a time-variant currency period.
References Cited (Backward Citations)
No citation records indexed.
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