Capturing data of a database system

• US 5,175,849 A
• Filed: 12/20/1990
• Issued: 12/29/1992
• Est. Priority Date: 07/28/1988
• Status: Expired due to Term

• Current Assignee: Amdahl Corporation (Fujitsu Limited)
• Original Assignee: Amdahl Corporation (Fujitsu Limited)
• Inventors: Schneider, Frederick W.
• Primary Examiner(s): Anderson, Lawrence E.
• Assistant Examiner(s): Lim, Krisna
• Application Number:
  US07/632,604
• Time in Patent Office: 740 Days
• Field of Search: 395/600, 395/425, 395/575
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive
• CPC Class Codes: G06F 2201/80 Database-specific techniques
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

To create a snapshot copy of selected elements of a database in a data processing system, the selected elements are copied sequentially to a secondary storage device. During the copying operation, when a task requests to delete one of the selected elements from the database before it is copied to the secondary storage device, a record is made to identify the requested element, the task is allowed to continue processing. After the element has been copied to the secondary storage device, the identified element will be deleted based upon the record. Also, during the creation of the copy, when a task requests to update one of the selected elements, a duplicate copy of the requested element is created and the task is allowed to update the requested element. When it is time to copy the requested element to the secondary storage device, the duplicate copy will be used.

Claims

1. In a data processing system having a database comprising a plurality of elements being stored in at least one storage device, each of the elements being asynchronously updatable and deletable by tasks operating within the data processing system, a computer implemented method for creating a snapshot copy of selected elements of the database, comprising the steps of:

copying sequentially said selected elements from said storage device storing said selective elements into a secondary storage device;

identifying, in response to a request from a task operating in said data processing system to delete one of said selected elements while said sequential copying of said selected elements is in progress, in a first record, stored within said data processing system, said selected element to be deleted if said selected element has not bee copied to said secondary storage device at the time when said request for deletion was made;

deleting said identified selected element as identified in said first record after said identified selected element has been copied to said secondary storage device;

creating and storing in a temporary storage, in response to a request from a task operating within said data processing system to update one of said selected elements while said sequential copying of said selected elements is in progress, a duplicate copy of said selected element to be updated before said selected element is updated if said selected element has not bee copied to said secondary storage device at the time when said request to update was made;

identifying said selected element in a second record stored within said data processor system if a duplicate copy of said selected element has been stored in said temporary storage;

updating said selected element to be updated stored in said storage device;

copying from said temporary storage said duplicate copy of a said selected element identified in said second record to said second storage device when said update selected element would have been sequentially copied to said second storage device.

2. The method of claim 1, further comprising the steps of providing and periodically updating a map which identifies elements selected to be included in said snapshot copy.

3. The method of claim 2, comprising the steps of copying and storing said map in response to said request to create said snapshot copy thereby identifying said selected elements to be included in said snapshot copy.

4. The method of claim 3, wherein the step of copying said map includes the steps of inhibiting access to the database immediately before making said copy of said map and immediately enabling access to the database after completion of said copy of said map.

5. The method as in claim 1 further including the steps of detecting a synchronization point and initiating the creation of said snapshot copy of said database when said synchronization point is detected.

6. The method as in claim 5, wherein said synchronization point is detected using a two-phase commit protocol.

7. In a data processing system having a database comprising a plurality of elements being stored in at least one storage device, each of the elements being asynchronously updatable and deletable by tasks operating within the data processing system, a computer implemented method for creating a snapshot copy of selected elements of the database, comprising the steps of:

a. providing and continuously maintaining a map to identify elements to be selected for inclusion in a snapshot copy of the database;

b. in response to a command from said data processing system to create a snapshot copy of the database performing the steps of;

b1. creating a copy of said map to identify said elements selected for said snapshot copy; and

b2. disabling access to the database only during the period of time said map is being copied;

c. copying said selected elements identified in said map copy sequentially into a secondary storage device;

d. in response to a request from a task operating within said data processing system to delete a said selected element while said sequential copying of said selected elements is in progress performing the steps of;

d1. identifying said selected element to be deleted in a first record stored in said data processing system if said selected element to be deleted has not been copied into said secondary storage device; and

d2. deleting each said identified selected element in said first record after each said identified selected element has been copied into said secondary storage device; and

e. in response to a request from a task operating within said data processing system to update a said selected element while said sequential copying of said selected elements is in progress performing the steps of;

e1. creating and storing in a temporary storage a temporary copy of said selected element to be updated before said selected element is updated if said selected element has not been copied to said secondary storage device;

e2. identifying in a second record stored in said data processing system a said selected element to be updated if said temporary copy of said selected element has been stored in said temporary storage;

e3. updating said selected element to be stored in said storage device;

e4. copying from said temporary storage said temporary copy of a said selected element, identified in said second record, to said secondary storage device when said updated selected element would have been sequentially copied to said secondary storage device.

8. The method as in claim 7, further including the steps of detecting a synchronization point and initiating the creation of said snapshot copy when said synchronization point is detected.

9. The method as in claim 8, wherein said synchronization point is detected using a two-phase commit protocol.

10. In a data processing system having a database comprising a plurality of elements being stored in at least one storage device, each of the elements being asynchronously updatable and deletable by tasks operating within the data processing system, an apparatus for creating a snapshot copy of selected elements of the database, comprising:

first means, in response to a request from said data processing system to create said snapshot copy, fir copying said selected elements sequentially into a secondary storage device;

first recording means, in response to a request from a task operating in said data processing system to delete one of said selected elements and where said deletion request occurs when said first means is in the process of sequentially copying said snapshot copy, for identifying said selected element to be deleted if said selected element has not been copied to said secondary storage device;

second means responsive to said first recording means for deleting each said identified selected element as identified by said first recording means after each said identified selected element has been copied to said secondary storage device;

temporary storage means;

third means, in response to a task operating in said data processing system requesting to update one of said selected elements and where said update request occurs when said first means is in the process of copying said snapshot copy, for creating and storing in said temporary storage means a temporary copy of said selected element to be updated before said selected element is updated if said selected element has not been copied to said secondary storage device;

second recording means for identifying said selected element to be updated for which a temporary copy has been stored in said temporary storage by said third means;

fourth means for updating said selected element to be stored in said storage device;

fifth means responsive to said second recording means for copying from said temporary storage said temporary copy of said selected element as identified by said second recording means into said secondary storage device when said updated selected element would have been sequentially copied into said secondary storage device.

11. The apparatus as in claim 10, further comprising means for maintaining a map of elements selected to be included in said snapshot copy of said database.

12. The apparatus as in claim 11, comprising fifth means, in response to said request to create said snapshot copy of said database, for copying said map to identify said selected elements to be included in said snapshot copy.

13. The apparatus of claim 12, wherein said fifth means includes sixth means for inhibiting access to said database during the period of time that said map is being copied.

14. The apparatus as in claim 10, further including seventh means for detecting a synchronization point and eighth means for initiating the creation of said snapshot copy when said synchronization point is detected.

15. The apparatus as in claim 14, wherein said synchronization point detected by said seventh means is detected using a two-phase commit protocol.

16. In a data processing system having a database comprising a plurality of elements being stored in at least one storage device, each of the elements being asynchronously updatable and deletable by tasks operating within the data processing system, an apparatus for creating a snapshot copy of selected elements of the database, comprising:

a. first means for identifying in a map selected elements which will be selected to be included in a snapshot copy of said database;

b. second means, in response to a request from said data processing system to create said snapshot copy of the database, for creating a temporary copy of said map to identify said selected elements to be included in said requested snapshot copy;

c. third means for disabling access to the database during the period of time during which said second means is creating said temporary map;

d. fourth means for sequentially copying said selected elements identified in said temporary map into a secondary storage device;

e. first record means, response to a request from a task operating within said data processing system to delete said selected element when said request is made while said fourth means is in the process of copying all said selected elements, for identifying said selected element to be deleted if said selected element to be deleted has not been copied into said secondary storage device;

f. fifth means for deleting said identified selected element as identified by said first record means after said identified selected element has been copied to said secondary storage device;

g. temporary storage;

h. sixth means, responsive to a request from a task operating within said data processing system to update a said selected element when said request to update a selected element is made while said fourth means is in the process of sequentially copying all said selected elements, for creating and storing in said temporary storage a temporary copy of said selected element to be updated before said selected element to be updated is updated;

i. second record means for identifying said selected element to be updated if said temporary copy of said selected element has been stored in said temporary storage by said sixth means;

j. seventh means for updating said selected element to be stored in said storage device; and

k. eighth means for copying from said temporary storage said temporary copy of a said selected element as identified in said second record means to said secondary storage device when said updated selected element would have been sequentially copied into said second secondary device.

17. The apparatus as in claim 16, further including a ninth means for detecting a synchronization point and for initiating the creation of said snapshot copy when said synchronization point is detected.

18. The apparatus as in claim 17, wherein said synchronization point detected by said ninth means is detected using the two-phase commit protocol.