Data set backup in a shared environment

• US 6,061,769 A
• Filed: 01/22/1997
• Issued: 05/09/2000
• Est. Priority Date: 09/27/1995
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Scott, Jonathan Andrew, Rose, Ian Hulme, Strickland, Jimmy Paul, Kapulka, Kenneth Michael
• Primary Examiner(s): Nguyen, Hiep T
• Application Number:
  US08/793,006
• Time in Patent Office: 1,203 Days
• Field of Search: 711/161, 711/162, 714/6, 714/20, 707/202, 707/204, 713/502
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1461 Backup scheduling policy
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A method of taking a backup copy of a data set, for use with a log, with the data set being open for update by multiple updaters is described. A point on the log is identified (Recovery Time) from which it can be ensured that all data updates identified on the log have been written by an updater from buffers to the data set. This is done by recording a Recovery Time, and then not taking the backup until all the updaters have confirmed that they have written all updates from buffers to the data set. In addition, if tokens are used on the log to avoid having to identify the data set in full, then these are also written to the log before the update is taken.

Claims

1. A method, for use in a backup manager, of taking a backup copy of a data set for use, together with a log, in forward recovery of said data set, updaters updating a part of the data set by copying said part of the data set into buffers, performing an update on the copy in said buffers, and copying the updated buffers contents to said part of the data set, the method comprising the steps, by the backup manager, of:

taking a backup copy of said data set;

characterized in that;

the data set is open for update by multiple updaters; and

the method further comprises the steps, prior to said taking a backup copy, of;

indicating the current time as a Recovery Time; and

waiting until all updaters have copied all said updated buffers contents to said part of the data set.

2. A method as claimed in claim 1, wherein before said waiting step, all updaters are requested to copy all data in said buffers to said part of the data set.

3. A method as claimed in claim 2, wherein records written in the log include tokens, each token corresponding to one of a plurality of data sets, the correspondence being achieved by means of tie-up records written in the log, the method further comprising the step, prior to taking a backup copy, of requesting all updaters to write tie-up records to the log for all tokens in use that relate to the dat set being copied.

4. A method as claimed in claim 2, wherein:

before said requesting step, said backup manager notifies a data set manager that a backup is to be taken;

said data set manager requests all updaters to copy all data in said buffers; and

said data set manager notifies said backup manager that all updaters have copied all data in said buffers.

5. Data processing apparatus comprising:

means for storing a data set;

means for maintaining a log for use in forward recovery of said data set;

means for updating a part of said data set by copying said part of the data set into buffers, performing an update on the copy in said buffers, and copying the updated buffers contents to said part of the data set;

a backup manager for taking a backup copy of said data set;

characterised in that;

the data set is open for update by multiple means for updating;

the apparatus comprises a plurality of said means for updating; and

the backup manager further comprises means for indicating a current time prior to starting to take a backup copy as a Recovery Time;

means for waiting until all the updating means have copied all said updated buffers contents to said part of the data set; and

means for initiating a backup copy on completion of copying by the updating means.

6. In a computer system having an online backup manager, a method for backing up a data set stored on a storage device, a plurality of updaters making updates to the data set, the method performed by the backup manager comprising the steps of:

(a) designating a recovery time;

(b) maintaining at least one log comprising a plurality of records corresponding to the updates for the data set;

(c) waiting until all updates by the plurality of updaters from prior to the recovery time have been written to the data set stored on the storage device; and

(d) after completing steps (a) through (c), making a backup copy of the data set, wherein the backup copy and the at least one log are used in a forward recovery of the data set.

7. The method as claimed in claim 6 further comprising the step of:

(e) prior to step (c), sending a request to all of the plurality of updaters to write all updates to the data set stored on the storage device.

8. The method as claimed in claim 7, wherein the updates are for a plurality of data sets, each of the log records including a token corresponding to one of the plurality of data sets, wherein a tie-up record provides the correspondence between the token and the one of the plurality of data sets.

9. The method as claimed in claim 8 further comprising the step of:

(f) prior to step (c), sending a request to all updaters to write tie-up records to the log for all the tokens in use that correspond to the data set being copied.

10. The method as claimed in claim 6 further comprising the step of:

(g) prior to step (c), the backup manager sending a notification to a data set manager that the backup of the data set is to be made;

(h) the data set manager sending a request to all updaters to write all updates to the data set stored on the storage device; and

(i) the data set manager sending a notification to the backup manager that all updaters have written all updates prior to the recovery time to the data set on the storage device.

11. The method as claimed in claim 6 wherein all the updates from each updater are maintained in a separate log for each updater.

12. The method as claimed in claim 6 wherein a single log is maintained for all the updates from all the updaters.

13. The method as claimed in claim 6 wherein all updates for a group of updaters are maintained in a separate log for each group of updaters.

14. The method as claimed in claim 6 wherein the data set remains available to the updaters during step (a) through step (d).

15. An online backup system for a computer system having a data set stored on a storage device, and a plurality of updaters making updates to the data set, the online backup system comprising:

at least one log comprising a plurality of records corresponding to the updates to the data set; and

a backup manager for making a backup copy of the data set after designating a recovery time, and waiting until all updates by the plurality of updaters prior to the recovery time have been written to the data set stored on the storage device, wherein the backup copy and the at least one log are used in a forward recovery of the data set.

16. The system as claimed in claim 15 wherein the backup manager sends a request to all of the plurality of updaters to write all updates to the data set stored on the storage device.

17. The system as claimed in claim 16 wherein the updates are for a plurality of data sets, each of the log records including a token corresponding to one of a plurality of data sets, wherein a tie-up record provides the correspondence between the token and the one of the plurality of data sets.

18. The system as claimed in claim 17 wherein the backup manager sends a request to all updaters to write tie-up records to the log for all the tokens in use that correspond to the data set being copied.

19. The system as claimed in claim 15 further comprising;

a data set manager, in response to a notification from the backup manager, sending a request to all updaters to write all updates to the data set stored on the storage device, the data set manager sending a notification to the backup manager when all updaters have written all updates from prior to the recovery time to the data set on the storage device.

20. The system as claimed in claim 15 wherein all the updates from each updater are maintained in a separate log for each updater.

21. The system as claimed in claim 15 wherein a single log is maintained for all the updates from all the updaters.

22. The system as claimed in claim 15 wherein all updates for a group of updaters are maintained in a separate log.

23. The system as claimed in claim 15 wherein the data set remains available to the updaters during the making of the backup copy of the data set.