US5581753A
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Method for providing session consistency guarantees
Assignee: Gula Consulting LLC
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Filing: 1994-09-28
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Granted: 1996-12-03
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Expires: 2014-09-28
Abstract
Abstract The present invention provides client-selected consistency guarantees to clients of a weakly consistent replicated database on a per "session" basis. The clients have access to utilities which allow the clients to, individually or collectively, define a "session" over which the selected guarantees are enforced. A "session" is broadly defined as a sequence of logically related Reads and Writes to the database. Sessions are initiated and terminated substantially independently of other sessions which may exist concurrently. Clients are allowed, however, to clone sessions and/or merge sessions with other clients. Clients select a minimum relevant subset of guarantees from among a set of pre-defined consistency guarantees, where "relevancy" is a client determined factor. At any given time, the system may be enforcing a number of different combinations of consistency guarantees. The guarantees ensure that all clients participating in a particular session view the database as having certain conditions of data consistency--the consistency of which is only provided with respect to the participants' Read and Write requests. Clients are allowed to downgrade their selected guarantees during the course of their sessions. One implementation of the present invention permits the selection of any one of four consistency guarantees.
Inventors
- 👤 Douglas B. Terry
- 👤 Alan J. Demers
- 👤 Karin Petersen
- 👤 Michael J. Spreitzer
- 👤 Marvin M. Theimer
- 👤 Brent B. Welch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:17
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/14; G06F11/1402; G06F16/00; G06F16/20; G06F16/23; G06F16/2365; Y; Y10; Y10S; Y10S707/00; Y10S707/99951; Y10S707/99952
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
207 words
In a database system having a plurality of servers, a plurality of clients, where at least some of said clients may access different servers at different times, including times when said servers contain inconsistent data values; said servers storing weakly consistent replicated data; said data being accessible and updatable by said clients; and said data, once updated, being propagated by servers having said updated data to servers that do not have said updated data: a method for providing relevant consistency guarantees for said data to every client participating in any session on a per session basis with respect to access and update requests belonging to each respective session, the steps of said method comprising: A) defining a plurality of sessions, such that each of said sessions is composed of database access and update requests of at least one client; B) selecting a client specified relevant subset of consistency guarantees for each session from a set of predefined, mutually distinguishable guarantees, where the relevancy of a given guarantee is decided by at least one of said clients; and C) enforcing the selected guarantees for said at least one client during the course of said session even when said at least one client accesses different servers during the session.
Claim 2
Dependent Claim
207 words
In a database system having a plurality of servers, a plurality of clients, where at least some of said clients may access different servers at different times, including times when said servers contain inconsistent data values; said servers storing weakly consistent replicated data; said data being accessible and updatable by said clients; and said data, once updated, being propagated by servers having said updated data to servers that do not have said updated data: a method for providing relevant consistency guarantees for said data to every client participating in any session on a per session basis with respect to access and update requests belonging to each respective session, the steps of said method comprising: A) defining a plurality of sessions, such that each of said sessions is composed of database access and update requests of at least one client; B) selecting a client specified relevant subset of consistency guarantees for each session from a set of predefined, mutually distinguishable guarantees, where the relevancy of a given guarantee is decided by at least one of said clients; and C) enforcing the selected guarantees for said at least one client during the course of said session even when said at least one client accesses different servers during the session.
Claim 3
Dependent Claim
26 words
The method for providing consistency guarantees as recited in claim 1 wherein the step of defining a session further comprises the step of initiating a session.
Claim 4
Dependent Claim
26 words
The method for providing consistency guarantees as recited in claim 1 wherein the step of defining a session further comprises the step of terminating a session.
Claim 5
Dependent Claim
26 words
The method for providing consistency guarantees as recited in claim 1 wherein the step of defining a session further comprises the step of cloning a session.
Claim 6
Dependent Claim
28 words
The method for providing consistency guarantees as recited in claim 1 wherein the step of defining a session further comprises the step of merging at least two sessions.
Claim 7
Dependent Claim
34 words
The method for providing consistency guarantees as recited in claim 1 wherein the step of defining a session further comprises the step of downgrading the set of guarantees during the course of a session.
Claim 8
Dependent Claim
31 words
The method for providing consistency guarantees as recited in claim 1 wherein said clients update data and access data at said servers by issuing a WRITE and a READ command respectively.
Claim 9
Dependent Claim
45 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Read R follows Write W in a session and R is performed at server S at time t, then W is included in DB(S,t).
Claim 10
Dependent Claim
52 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Read R1 occurs before R2 in a session and R1 accesses server S1 at time t1 and R2 accesses server S2 at time t2, then RelevantWrites(S1,t1,R1) is a subset of DB(S2,t2).
Claim 11
Dependent Claim
60 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Read R1 precedes Write W2 in a session and R1 is performed at server S1 at time t1, then, for any server S2, if W2 is in DB(S2) then any W1 in RelevantWrites(S1,t1,R1) is also in DB(S2) and WriteOrder(W1,W2).
Claim 12
Dependent Claim
58 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Read R1 precedes Write W2 in a session and R1 is performed at server S1 at time t1, then, for any server S2, if W2 is in DB(S2) then any W1 in RelevantWrites(S1,t1,R1) is also in DB(S2).
Claim 13
Dependent Claim
56 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Read R1 precedes Write W2 in a session and R1 is performed at server S1 at time t1, then, for any server S2, if W2 is in DB(S2) then, for any W1 in RelevantWrites(S1,t1,R1), WriteOrder(W1,W2).
Claim 14
Dependent Claim
46 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Write W1 precedes Write W2 in a session, then, for any server S2, if W2 in DB(S2) then W1 is also in DB(S2) and WriteOrder(W1,W2).
Claim 15
Dependent Claim
44 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Write W1 precedes Write W2 in a session, then, for any server S2, if W2 in DB(S2) then W1 is also in DB(S2).
Claim 16
Dependent Claim
40 words
The method for providing consistency guarantees as recited in claim 7 wherein one of said session guarantees comprises the condition: if Write W1 precedes Write W2 in a session, then, for any server S2, if W2 in DB(S2) then WriteOrder(W1,W2).
Claim 17
Dependent Claim
42 words
The method for providing consistency guarantees as recited in claim 1 wherein the step of enforcing the guarantees further comprises the steps of: locating at least one reachable server; and discovering whether said at least one reachable server satisfies the selected guarantees.
Claim 18
Dependent Claim
30 words
The method for providing consistency guarantees as recited in claim 16 wherein the step of discovering further comprises the step of informing the client if no suitable server is found.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-12-03 | 2000-06-03 | 2000-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-12-03 | 2004-06-03 | 2004-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-12-03 | 2008-06-03 | 2008-12-03 | $7700.00 | Window Closed / Lapsed |