Suspending a result set and continuing from a suspended result set for transparent session migration

• US 20060036617A1
• Filed: 04/01/2005
• Published: 02/16/2006
• Est. Priority Date: 08/12/2004
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Gollapudi, Sreenivas, Chatterjee, Debashish, Krishnaswamy, Srinath, Kaluskar, Sanjay, Chidambaran, Lakshminarayanan, Bastawala, Mehul D.
• Granted Patent: US 7,587,400 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/284 Relational databases
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A system, method, computer program and system for suspending a result set and continuing from a suspended result set for transparent session migration is disclosed. The rows from a row source are suspended into storage, so that after session migration, the client fetches can transparently continue from the suspended result set.

Claims

1. A method for suspending a cursor result set for transparently migrating a first session, the method comprising:

receiving notification the first session is selected for migration;

preparing to migrate, preparing including suspending cursor result sets for the first session;

determining if the first session is ready to migrate; and

migrating the first session.

2. The method of claim 1 wherein migrating comprises:

opening a second session;

copying the first session state to the second session;

connecting a client to the second session; and

breaking the client connection to the first session.

3. The method of claim 2, further comprising executing a fetch request on the suspended cursor result sets from the second session.

4. The method of claim 3, wherein executing the fetch request on the suspended cursor result sets comprises:

determining the location of a subject row of the result set; and

returning the subject row from the location.

5. The method of claim 2, wherein executing a call on the suspended result set via the second session is preceded by the same cursor executing a call on the result set via the first session.

6. The method of claim 2, wherein the client is unaware that a session is migrating or of a switch from the first session to the second session.

7. The method of claim 1, wherein suspending cursor result sets comprises storing the rows of each cursor, each cursor'"'"'s rows stored into a storage area associated with that cursor.

8. The method of claim 5, wherein the storage area comprises memory, persistent storage, or a combination of persistent storage and memory.

9. The method of claim 5, wherein the storage area includes all the rows in cursor result set.

10. The method of claim 1 in which a client accesses session data from the first session before migration has completed.

11. The method of claim 1 in which a client accesses session data from the first session after migration has completed.

20. The method of claim 2, wherein a user is unaware of the switch from the first session to the second session.

12. A method for suspending a cursor result set and continuing a suspended cursor result set for transparent session migration, the method comprising:

executing a query on a first session on a first server;

receiving notification the first session was selected for migration;

preparing to migrate the first session;

determining if ready to migrate the first session; and

migrating the first session.

13. The method of claim 12, wherein preparing to migrate comprises:

determining the result set is being fetched;

computing a set of constraint values for the cursor; and

suspending the result set of all cursors.

14. The method of claim 13, wherein preparing to migrate further comprising sending notification to the client of the selection for migration.

15. The method of claim 13, the suspending further comprising:

a) caching a row into a storage location;

b) determining if any of the set of constraint values have been exceeded;

c) determining if there are more rows to be suspended if the constraint values have not been exceeded; and

d) repeating a)-c) if there are more rows to be suspended.

16. The method of claim 12, wherein migrating comprises:

opening a second session on a second server;

copying the first session'"'"'s state information to the second session;

connecting the client to the second session; and

breaking connection between the client and the first session.

17. The method of claim 16, further comprising executing a call on the suspended result set data via a second session.

18. The method of claim 17, wherein the continuing the suspended cursor result set further comprises:

e) determining that the result set is suspended;

f) determining the location of a subject row of the result set;

g) repeating e)-g) until all the required rows have been fetched.

19. The method of claim 17, wherein executing a call on the suspended result set via a second session is preceded by the same cursor executing a call on the result set via the first session.

21. The method of claim 16, wherein suspending a result set comprises:

determining the result set is to be suspended;

storing a first row of the result set in a storage area; and

repeating the storing until all the required rows have been suspended.

22. The method of claim 21, wherein the suspending is performed in a manner so that the performance degradation of the returning rows to the client caused by the suspending is unnoticeable to a user.

23. The method of claim 12, wherein the suspended result set is transmitted from one node to another node.

24. The method of claim 12, wherein the executing query is a distributed SQL query.

25. The method of claim 12 wherein the query does not have to adjust any application parameters due to the migration.

26. The method of claim 12, wherein the transparent session migration is a cascaded transparent session migration.

27. A computer program product comprising a computer usable medium having executable code to execute a process for suspending a cursor result set and continuing a suspended cursor result set for transparent session migration, the process comprising:

executing a query on a first session on a first server;

receiving notification the session was selected for migration;

preparing to migrate;

determining if ready to migrate; and

migrating, when ready.

28. A system for suspending a cursor result set and continuing a suspended cursor result set for transparent session migration, comprising:

logic for executing a query on a first session on a first server;

logic for receiving notification the first session was selected for migration;

logic for preparing to migrate the first session;

logic determining if ready to migrate the first session; and

logic for migrating the first session.

29. A computer program product comprising a computer usable medium having executable code to execute a process for suspending a cursor result set for transparently migrating a first session, the process comprising:

executing a query on a first session on a first server;

receiving notification the first session was selected for migration;

preparing to migrate the first session;

determining if ready to migrate the first session; and

migrating the first session.

30. A system for suspending a cursor result set for transparently migrating a first session, the method comprising:

logic for receiving notification the first session is selected for migration;

logic for preparing to migrate, preparing including suspending cursor result sets for the first session;

logic for determining if the first session is ready to migrate; and

logic for migrating the first session.