SELECTIVELY READING DATA FROM CACHE AND PRIMARY STORAGE

• US 20100122026A1
• Filed: 01/21/2010
• Published: 05/13/2010
• Est. Priority Date: 09/19/2008
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Aya, Selcuk, Lee, Sue-Kyoung, Goyal, Kiran B., Fan, Susy, Choudhury, Nilesh, Shetler, Timothy L., Loaiza, Juan R., Tsukerman, Alexander, Erlikhman, Boris, Baddepudi, Bharat C.V., Umamageswaran, Kothanda, Kumar, Poojan, Panchaksharaiah, Umesh
• Granted Patent: US 10,430,338 B2
• Time in Patent Office: Days
• US Class Current: 711/113
• CPC Class Codes: G06F 12/0811 with multilevel cache hierarchies
• CPC Class Codes: G06F 12/084 with a shared cache
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 12/0888 using selective caching, e.g. bypass
• CPC Class Codes: G06F 16/24552 Database cache management
• CPC Class Codes: G06F 16/24557 Efficient disk access during query execution

Abstract

Techniques are provided for using an intermediate cache to provide some of the items involved in a scan operation, while other items involved in the scan operation are provided from primary storage. Techniques are also provided for determining whether to service an I/O request for an item with a copy of the item that resides in the intermediate cache based on factors such as a) an identity of the user for whom the I/O request was submitted, b) an identity of a service that submitted the I/O request, c) an indication of a consumer group to which the I/O request maps, d) whether the I/O request is associated with an offloaded filter provided by the database server to the storage system, or e) whether the intermediate cache is overloaded. Techniques are also provided for determining whether to store items in an intermediate cache in response to the items being retrieved, based on logical characteristics associated with the requests that retrieve the items.

Claims

1. A method comprising:

receiving, from a software application, at a storage system, one or more I/O requests to retrieve items involved in an operation that targets data that resides on primary storage managed by the storage system; and

in response to the one or more I/O requests, the storage system providing a first set of items required by the operation from the primary storage, and a second set of items required by the operation from an intermediate cache managed by the storage system;

wherein the storage system only issues I/O requests to the intermediate cache for the second set of items after determining that the intermediate cache is not overloaded.

2. The method of claim 1 wherein:

the software application is a database server; and

the operation is a scan operation of a database object managed by the database server.

3. The method of claim 1 wherein the storage system determines whether the intermediate cache is overloaded based on how many I/O requests have been queued to be processed by the intermediate cache.

4. The method of claim 1 wherein the storage system retrieves the first set of items from primary storage concurrently with the storage system retrieving the second set of items from the intermediate cache.

5. A computer-readable storage storing instructions which, when executed by one or more processors, cause:

receiving, from a database server, at a storage system, one or more I/O requests to retrieve items involved in a scan operation that targets a database object that resides on primary storage managed by the storage system; and

in response to the one or more I/O requests, the storage system providing a first set of items required by the scan operation from the primary storage, and a second set of items required by the scan operation from an intermediate cache managed by the storage system;

wherein the storage system only issues I/O requests to the intermediate cache for the second set of items after determining that the intermediate cache is not overloaded.

6. The computer-readable storage of claim 5 wherein the storage system determines whether the intermediate cache is overloaded based on how many I/O requests have been queued to be processed by the intermediate cache.

7. The computer-readable storage of claim 5 wherein the first set of items are retrieved from primary storage concurrently with the second set of items being retrieved from the intermediate cache.

8. A method comprising:

receiving from a database server, at a storage system, an I/O request for an item that resides on primary storage, of which a copy currently resides in an intermediate cache;

in response to the request, the storage system performing the steps of;

determining whether to service the I/O request with the copy of the item that resides in the intermediate cache based on one or more factors, wherein the one or more factors include at least one of;

a) an identity of the user for whom the I/O request was submitted,

b) an identity of a service that submitted the I/O request,

c) an indication of a consumer group to which the I/O request maps,

d) whether the I/O request is associated with an offloaded filter provided by the database server to the storage system;

or

e) whether the intermediate cache is overloaded;

in response to determining, based on one or more factors, that the I/O request should be serviced with the copy of the item that resides in the intermediate cache, responding to the I/O request with the copy of the item that resides the intermediate cache without retrieving the item from primary storage;

wherein the method is performed by one or more computing devices.

9. The method of claim 8 wherein the one or more factors further include whether the cache is overloaded.

10. The method of claim 8 wherein the I/O request is for a scan operation being performed by the database server.

11. The method of claim 10 wherein the storage system provides some items for the scan operation from primary storage, and other items for the scan operation from the intermediate cache.

12. The method of claim 10 wherein the storage system applies filter criteria, provided to the storage system by the database server, to items involved in the scan operation.

13. The method of claim 8 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on an identity of the user for whom the I/O request was submitted.

14. The method of claim 8 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on an identity of a service that submitted the I/O request.

15. The method of claim 8 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on an indication of a consumer group to which the I/O request maps.

16. The method of claim 8 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on whether the I/O request is associated with an offloaded filter provided by the database server to the storage system.

17. A method comprising:

receiving from a database server, at a storage system, an I/O request for an item that resides on primary storage but that does not currently reside in an intermediate cache;

in response to the request, the storage system performing the steps of;

retrieving the item from the primary storage;

providing the item to the database server;

determining whether to store a copy of the item in the intermediate cache based on one or more factors, wherein the one or more factors include at least one of;

a) an identity of the user for whom the I/O request was submitted,

b) an identity of a service that submitted the I/O request,

c) an indication of a consumer group to which the I/O request maps, or

d) whether the I/O request is associated with an offloaded filter provided by the database server to the storage system;

in response to determining that the copy of the item should be stored in the intermediate cache based on one or more factors, storing the copy of the item in the intermediate cache;

wherein the method is performed by one or more computing devices.

18. The method of claim 17 wherein determining whether to store the copy of the item in the intermediate cache is based, at least in part, on an identity of the user for whom the I/O request was submitted.

19. The method of claim 17 wherein determining whether to store the copy of the item in the intermediate cache is based, at least in part, on an identity of a service that submitted the I/O request.

20. The method of claim 17 wherein determining whether to store the copy of the item in the intermediate cache is based, at least in part, on an indication of a consumer group to which the I/O request maps.

21. The method of claim 17 wherein determining whether to store the copy of the item in the intermediate cache is based, at least in part, on whether the I/O request is associated with an offloaded filter provided by the database server to the storage system.

22. A computer-readable storage storing instructions which, when executed by one or more processors, cause:

receiving from a database server, at a storage system, an I/O request for an item that resides on primary storage, of which a copy currently resides in an intermediate cache;

in response to the request, the storage system performing the steps of;

determining whether to service the I/O request with the copy of the item that resides in the intermediate cache based on one or more factors, wherein the one or more factors include at least one of;

a) an identity of the user for whom the I/O request was submitted,

b) an identity of a service that submitted the I/O request,

c) an indication of a consumer group to which the I/O request maps,

d) whether the I/O request is associated with an offloaded filter provided by the database server to the storage system;

or

e) whether the intermediate cache is overloaded;

in response to determining, based on one or more factors, that the I/O request should be serviced with the copy of the item that resides in the intermediate cache, responding to the I/O request with the copy of the item that resides the intermediate cache without retrieving the item from primary storage;

wherein the method is performed by one or more computing devices.

23. The computer-readable storage of claim 22 wherein the one or more factors further include whether the cache is overloaded.

24. The computer-readable storage of claim 22 wherein the I/O request is for a scan operation being performed by the database server.

25. The computer-readable storage of claim 24 wherein the storage system provides some items for the scan operation from primary storage, and other items for the scan operation from the intermediate cache.

26. The computer-readable storage of claim 24 wherein the storage system applies filter criteria, provided to the storage system by the database server, to items involved in the scan operation.

27. The computer-readable storage of claim 22 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on an identity of the user for whom the I/O request was submitted.

28. The computer-readable storage of claim 22 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on an identity of a service that submitted the I/O request.

29. The computer-readable storage of claim 22 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on an indication of a consumer group to which the I/O request maps.

30. The computer-readable storage of claim 22 wherein determining whether to service the I/O request with the copy of the item that resides in the intermediate cache is based, at least in part, on whether the I/O request is associated with an offloaded filter provided by the database server to the storage system.

31. A computer-readable storage storing instructions with, when executed by one or more processors, cause:

receiving from a database server, at a storage system, an I/O request for an item that resides on primary storage but that does not currently reside in an intermediate cache;

in response to the request, the storage system performing the steps of;

retrieving the item from the primary storage;

providing the item to the database server;

determining whether to store a copy of the item in the intermediate cache based on one or more factors, wherein the one or more factors include at least one of;

a) an identity of the user for whom the I/O request was submitted,

b) an identity of a service that submitted the I/O request,

c) an indication of a consumer group to which the I/O request maps, or

d) whether the I/O request is associated with an offloaded filter provided by the database server to the storage system;

in response to determining that the copy of the item should be stored in the intermediate cache based on one or more factors, storing the copy of the item in the intermediate cache;

wherein the method is performed by one or more computing devices.

32. A storage system comprising:

primary storage for storing items for a database object;

an intermediate cache;

a mechanism for receiving, from a database server, one or more I/O requests to retrieve items involved in a scan operation that targets the database object;

wherein the mechanism is configured to respond to the one or more I/O requests by providing a first set of items required by the scan operation from the primary storage, and a second set of items required by the scan operation from the intermediate cache;

wherein the mechanism only issues I/O requests to the intermediate cache for the second set of items after determining that the intermediate cache is not overloaded.