Composite locking of objects in a database

• US 6,708,195 B1
• Filed: 03/12/1999
• Issued: 03/16/2004
• Est. Priority Date: 10/02/1998
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Corrigan, Kevin Patrick, Hewitt, Dale Robinson, Borman, Samuel David
• Primary Examiner(s): Follansbee, John
• Assistant Examiner(s): Ho, The Thanh
• Application Number:
  US09/267,586
• Time in Patent Office: 1,831 Days
• Field of Search: 709/315, 709/316, 709/104, 707/8, 707/103
• US Class Current: 718/102
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

In a multi-user environment, a method of controlling access to objects is required, such that updates performed by one user are not overwritten by simultaneous updates by another user. There is provided a method of controlling access to objects and containers, each representing a group of objects, in a multi-user environment whereby lock states of the objects and lock states of the containers are stored in a computer system, said method comprising the steps of: accepting a request for access to an object or a container; deciding access based on the lock state for that object or container, the lock state of a container if the request is for an object contained within that container, and the lock state of objects grouped within a container if the request is for a container object; and sending a message to the requester granting or denying access to said object or container object. Updates performed by one user on an object or a container are not overwritten by simultaneous updates by another user. The above supports units of work in a GUI session where a unit of work could be updating a single object, viewing a single object or copying or deleting a container of objects. This extends to manipulating entire voice applications which consist of many containers and other objects.

Claims

1. A method of controlling access to objects and containers, each representing a group of objects, in a multi-user environment whereby lock states of the objects and lock states of the containers are stored in a computer system, said method comprising the steps of:

accepting a request from a user for access to an object and a container, wherein each of said users has multiple sessions, and each of said sessions can own different lock states;

deciding access to the object and container based on;

the lock state owned by one of said sessions for that object or container; and

either, the lock state of a container if the request is for an object contained within that container, or the lock state of objects grouped within a container if the request is for a container wherein said container comprise real containers and conceptual containers; and

sending a message to the requester granting or denying access to said object or said container.

2. A method as claimed in claim 1 further comprising storing the lock states for containers and lock states for objects in a common format.

3. A method as claimed in claim 2 wherein the lock state for a container or an object is stored in a record in a table.

4. A method as claimed in claim 3 wherein the record comprises a container name field and an object name field containing a string expression.

5. A method as claimed in claim 4 wherein the lock state stored is an exclusive lock.

6. A method as claimed in claim 5 whereby the lock state comprises a non-exclusive lock state associated with a user session.

7. A method as claim in claim 6 wherein the non-exclusive lock state comprises a read lock.

8. A method as claim in claim 7 wherein more than one non-exclusive lock state may be associated with a lock entry.

9. A method as claim in claim 8 wherein multiple non-exclusive lock states may be stored in a linked list comprising linked records associated with record in a lock table.

10. A method of controlling access to objects and containers stored in a multi-user computer system comprising:

providing users access to said objects and containers;

identifying multiple sessions for each of said users accessing said objects and containers, wherein each of said sessions can own different lock status; and

restricting said access to said objects and containers based on the lock state owned by one of said sessions for that object or container; and

either, the lock state of a container if the request is for an object contained within that container, or the lock state of objects grouped within a container if the request is for a container, wherein said container comprise real containers and conceptual containers.

11. The method in claim 10, wherein said sessions comprise at least one of an interactive session and a background session.

12. The method in claim 11 further comprising preventing a user from acquiring an exclusive lock on both said interactive session and said background session with respect to a given object.

13. The method in claim 10, wherein said objects comprise real objects and conceptual objects.

14. The method in claim 10, wherein said locks restrict access to said objects and collections of said objects.

15. The method in claim 14, wherein said locks for said objects and said collection have the same format.

16. A method of controlling access to objects and containers stored in a multi-user computer system comprising:

providing users access to said objects and containers;

identifying multiple sessions for each of said users accessing said objects and containers, wherein each of said sessions has a unique session identifier, and each of said sessions can own different lock states; and

restricting said access to said objects and containers using locks, wherein each of said locks is owned by one session identifier for that object or container; and

either, the lock state of a container if the request is for an object contained within that container, or the lock state of objects grouped within a container if the request is for a container, wherein said container comprise real containers and conceptual containers.

17. The method in claim 16, wherein said sessions comprise at least one of an interactive session and a background session.

18. The method in claim 17, further comprising preventing a used from acquiring an exclusive lock on both said interactive session and said background session with respect to a given object.

19. The method in claim 16, wherein said objects comprise real objects and conceptual objects.

20. The method in claim 16, wherein said locks restrict access to said objects and collections of said objects.

21. A method of controlling access to entities in a multi-user environment whereby the entities are containers and objects, and lock states of the entities are stored in a common format comprising a record for a container name and a corresponding object name in a common database, said method comprising the steps of:

accepting an access request from a requestor for access to an entity wherein each requestor has multiple sessions, and each of said sessions can own different lock states;

deciding access to the entity based on;

the lock state of that object or container; and

either, the lock state of the container if the request is for an object contained within a container, or the lock state of the objects grouped within a container it the request is for a container;

wherein sad container comprise real containers and conceptual containers;

sending a message to the requestor granting or denying access to said entity; and

storing, if access is granted, a new lock state for the entity in the common format,

wherein, because said states of said containers and said objects are stored in said common format, the same access request may be performed on any entity irrespective of whether the entity is a container or an object.