EP0518639A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Lock management in a multi-system shared data environment
Assignee: International Business Machines Corp
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Filing: 1992-06-10
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Granted: —
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Expires: 2012-06-10
Abstract
Abstract In a combination of multiple concurrently-executing database management systems which share data storage resources, efficient lock processing for shared data is implemented by hiding from a global lock manager the distinction between transaction-interest and cache-interest locks that are processed at the DBMS level. The local lock manager of a DBMS, in response to a request for either type of lock, may issue a request to the global lock manager for a system-level lock without disclosing to the global lock manager the type of lock requested of the local lock manager. After receipt of the system level lock, the local lock manager can grant either transaction or cache interest locks locally on a data resource if the combined mode of locally-held locks on that data resource is greater than or equal to the requested mode.
Inventors
- 👤 Chandrasekaran Mohan
- 👤 Inderpal S. Narang
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 08:04
CPC Classifications
G; G06; G06F; G06F9/00; G06F9/06; G06F9/46; G06F9/52
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
170 words
A method for locking data resources in a shared data system including multiple database management systems (DBMS) connected to one or more data storage devices and to a global lock manager, the global lock manager receiving and granting requests for locks, each DBMS including a local lock manager for receiving, processing, and granting requests for a first type of lock (L lock) that indicates transaction interest in data resources and for a second type of lock (P lock) that indicates caching of a data resource for the DBMS, the method including the steps of: a. responsive to receipt of a first request for a lock of either type by a DBMS local lock manager for a data resource that is not cached at the DBMS, transmitting to the global lock manager a request for a lock (LP lock) that indicates DBMS interest in the data resource; and b. upon receipt by the local lock manager of a grant of the lock by the global lock manager, granting the first request.
Claim 2
Dependent Claim
229 words
The method of Claim 1, locks being granted in at least a first mode (X mode) denoting exclusive use of a data resource or a second mode (S mode) denoting shared use of a data resource, the X mode being of a relatively higher magnitude than the S mode: wherein, step (a) includes transmitting the request for the LP lock as a request in X mode if the first request denotes X mode or in S mode if the first request denotes S mode; and wherein, the grant received in step (b) is in the mode of the first request; the method further including: (c) responsive to receipt of a subsequent request for a lock of any type by the local lock manager for the data resource, determining a resultant mode of all- locks held on the data resource at the DBMS, the resultant mode being the highest mode magnitude of the held locks; (d.1) if the subsequent request is for a lock with a mode having a magnitude greater than the magnitude of the resultant mode, transmitting a request to the global lock manager for the LP lock on the data resource in the mode of the subsequent request; (d.2) upon receipt by the local lock manager of a grant of the LP lock in the requested mode, granting the subsequent request; otherwise, (e) granting the subsequent request.
Claim 3
Independent Claim
208 words
A method for inter-system data lock management in a combination including a global lock manager for processing system lock requests, one or more database storage resources, and a plurality of database management systems, each database management system (DBMS) including a local lock manager coupled to the global lock manager, and a cache manager coupled to the database storage resources for caching data resources at the DBMS, the method including the steps of: maintaining at a first DBMS a list of locks granted by the DBMS's local lock manager, the locks including a first type (L lock) denoting transaction interest in data resources and a second type (P lock) denoting cache management interest in data resources, each listed lock naming a data resource to which it applies; in response to receipt by the local lock manager of a request for a lock of either type for a data resource not named in the table: sending a request from the local to the global lock manager for an LP lock for the data resource; and placing the lock of either type in the list; upon receipt of a grant of the LP lock from the global lock manager, granting the requested lock of either type by the local lock manager.
Claim 4
Dependent Claim
121 words
The method of Claim 3, further including: maintaining at the global lock manager a list of LP locks granted by the global lock manager; at the global lock manager: (1) granting the requested LP lock if it is not in the list; (2) granting the requested LP lock if the list includes an LP lock owned by a second DBMS and the listed LP lock is compatible with the requested LP lock; or (3) if the list includes an LP lock owned by a second DBMS and the listed LP lock is incompatible with the requested LP lock, granting the requested LP lock after the listed LP lock is released by the second DBMS; and (4) listing the requested LP lock.
References Cited (Backward Citations)
No citation records indexed.
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