EP0398496A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method and system for efficient control of cached data in a distributed data processing system
Assignee: International Business Machines Corp
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Filing: 1990-04-10
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Granted: —
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Expires: 2010-04-10
Abstract
Abstract A system and method in which client access to data at a server is synchronised to keep the data consistent by ensuring that each portion of the data accessible for modification at a node is not accessible for reading or modification by any other node, while allowing portions of the data accessible only for reading to be accessible by any number of nodes. If a conflicting request arises from a different client the server must revoke data that has been previously distributed to a client. For a revoke_bytes request, all outstanding get_bytes are marked so that the bytes that are being requested to be revoked will be discarded when they do arrive at the client. To insure that read and write system calls on a file are performed in a serialisable fashion throughout a distributed environment, each machine at which a read is being performed must acquire a read token and each machine at which a write is being performed must acquire a read/write token from the server for the file. When any machine has a read/write token, no machine is allowed to have a read token, although any number of machines may have a read token at the same time. The server coordinates the distribution of these tokens by revoking all read tokens whenever a write token is requested and revoking the write token whenever any read token is requested.
Inventors
- 👤 Donavon William Johnson
- 👤 Stephen Paul Morgan
- 👤 Todd Allen Smith
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 03:32
CPC Classifications
G; G06; G06F; G06F16/00; G06F16/10; G06F16/18; G06F16/182; G06F16/184; G06F16/1844; G06F16/17; G06F16/176; G06F16/1767; G06F16/1774; Y; Y10; Y10S; Y10S707/00; Y10S707/99931; Y10S707/99938; Y10S707/99939
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
86 words
A method for controlling client machine access to a portion of a file stored at a server machine of a data processing system comprising: allowing transfer of the portion of the file to a plurality of client machines while each of the plurality of client machines has read-only access to the portion of the file; and allowing transfer of the portion of the file to only a single client machine at a time when the client machine has read/write access to the portion of the file.
Claim 2
Independent Claim
86 words
A method for controlling client machine access to a portion of a file stored at a server machine of a data processing system comprising: allowing transfer of the portion of the file to a plurality of client machines while each of the plurality of client machines has read-only access to the portion of the file; and allowing transfer of the portion of the file to only a single client machine at a time when the client machine has read/write access to the portion of the file.
Claim 3
Dependent Claim
56 words
A method as claimed in Claim 1, wherein the step of allowing transfer to the plurality of client machines further comprises issuing a read-only token to one of the plurality of client machines and requiring that the read-only token is at the one of the plurality of client machines for the duration of a read operation.
Claim 4
Dependent Claim
27 words
A method as claimed in Claim 2, further comprising revoking the read-only token in response to a request by the single client machine for a read/write token.
Claim 5
Independent Claim
52 words
A method as claimed in any preceding claim, further comprising issuing a read/write token to the single client machine in response to a request by the single client machine for a read/write token and requiring that the read/write token is at the single client machine for the duration of a write operation.
Claim 6
Dependent Claim
35 words
A method as claimed in Claim 4, further comprising revoking the read/write token in response to a request by one of the plurality of client machines for either a read/write token or a read-only token.
Claim 7
Independent Claim
50 words
A method as claimed in any preceding claim, further comprising revoking the portion of the file from the one of the plurality of client machines upon receipt by the server of a request for the portion of the file for read/write access or read-only access by any other client machine.
Claim 8
Dependent Claim
39 words
A method as claimed in Claim 6, wherein the step of revoking the portion of the file from the one of the plurality of client machines further comprises causing the client machine to discard the portion of the file.
Claim 9
Dependent Claim
70 words
A method as claimed in Claim 6, wherein the step of revoking the portion of the file from the single client machine further comprises causing the single client machine to send back to the server a first part of the portion of the file that has been changed by the single client machine and to discard a second part of the portion of the file which has not been changed.
Claim 10
Independent Claim
23 words
A method as claimed in any preceding claim, wherein the portion of file is a range of bytes of data in the file.
Claim 11
Independent Claim
94 words
A system for controlling client machine access to a portion of a file stored at a server machine of a data processing system comprising: first means for allowing transfer of the portion of the file to a plurality of client machines while each of the plurality of client machines has read-only access to the portion of the file; and second means connected to the first means for allowing transfer of the portion of the file to only a single client machine when the client machine has read/write access to the portion of the file.
Claim 12
Independent Claim
94 words
A system for controlling client machine access to a portion of a file stored at a server machine of a data processing system comprising: first means for allowing transfer of the portion of the file to a plurality of client machines while each of the plurality of client machines has read-only access to the portion of the file; and second means connected to the first means for allowing transfer of the portion of the file to only a single client machine when the client machine has read/write access to the portion of the file.
Claim 13
Dependent Claim
51 words
A system as claimed in Claim 10, wherein the first means further comprises means for issuing a read-only token to one of the plurality of client machines and for requiring that the read-only token is at the one of the plurality of client machines for the duration of a read operation.
Claim 14
Dependent Claim
36 words
A system as claimed in Claim 11, further comprising means connected to the first and second means for revoking the read-only token in response to a request by the single client machine for a read/write token.
Claim 15
Dependent Claim
58 words
A system as claimed in Claim 10, wherein the second means further comprises means for issuing a read/write token to the single client machine in response to a request by the single client machine for a read/write token and for requiring that the read/write token is at the single client machine for the duration of a write operation.
Claim 16
Dependent Claim
44 words
A system as claimed in Claim 13, further comprising means connected to the first and second means for revoking the read/write token in response to a request by one of the plurality of client machines for either a read/write token or a read-only token.
Claim 17
Independent Claim
60 words
A system as claimed in any of claims 10 to 14, further comprising means connected to the second means for revoking the portion of the file from the one of the plurality of client machines upon receipt by the server of a request for the portion of the file for read/write access or read-only access by any other client machine.
Claim 18
Dependent Claim
40 words
A system as claimed in Claim 15, wherein means for revoking the portion of the file from the one of the plurality of client machines further comprises means for causing the client machine to discard the portion of the file.
Claim 19
Dependent Claim
78 words
A system as claimed in Claim 16, wherein the means for revoking the portion of the file from the single client machine further comprises means for causing the single client machine to send back to the server a first part of the portion of the file that has been changed by the single client machine and for causing the single client machine to discard a second part of the portion of the file which has not been changed.
References Cited (Backward Citations)
No citation records indexed.
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