Continuous availability and efficient backup for externally referenced objects

• US 6,088,694 A
• Filed: 03/31/1998
• Issued: 07/11/2000
• Est. Priority Date: 03/31/1998
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Narang, Inderpal Singh, Burns, Randal Chilton
• Primary Examiner(s): AMSBURY, WAYNE P
• Application Number:
  US09/052,921
• Time in Patent Office: 833 Days
• Field of Search: 705/3, 705/2, 714/6, 707/1, 707/10, 707/8
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/1464 for networked environments
• CPC Class Codes: G06F 16/148 File search processing
• CPC Class Codes: G06F 16/1767 Concurrency control, e.g. optimistic or pessimistic approaches
• CPC Class Codes: G06F 16/20 of structured data, e.g. relational data
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99939 Privileged access
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A computing system provides continuous availability of data files that are maintained at a file management system and linked to a database management system (DBMS) through a Datalink data type, even while any particular file is being changed with DBMS append or update operations. When a file is linked, it is designated to be available for read-only operations. A user who wants to perform updates on a file gets a "check-out" copy of the file for updating operations, such that the original file remains linked to the database system while the copy is being updated and remains available to other users. The file management system includes a "check-in" function that receives the updated file, saves the updated file under a new name different from the original, updates the Datalink, generates new metadata for the updated file, and transactionally updates the file with its new metadata. In this way, data files are continuously available to all users through appending and updating actions. Since updating Datalinks requires the file management system to initiate backup, a "delta versioning" operation, which reduces the data needed to support backup operations, permits more efficient backup of data files and enables the continuously available files to be backed up and consistent.

Claims

1. A method of modifying a reference file that is maintained in file storage by a file manager and is referentially linked from a database management system (DBMS) while continuously maintaining the referential link to the reference file for DBMS users, the method comprising the steps of:

creating a copy of the reference file, while continuously permitting read-only access to the stored reference file to system users directly through the file manager;

performing file modification operations on the copy of the reference file;

permitting continuous availability of the stored reference file to DBMS users during the file modification operations by continuously maintaining the link to the stored reference file during the file modification operations;

introducing the modified reference file into the file storage;

updating the link between the DBMS and the reference file to refer to the modified reference file in a single transaction; and

performing automatic backup of the modified file by providing a copy of the modified reference file to a backup server.

5. A method as defined in claim 1, wherein the step of performing file modifications comprises performing file update operations.

6. A method as defined in claim 5, wherein the step of performing file modifications comprises the steps of:

performing a check-out operation by creating a check-out copy of the reference file and providing the check-out copy to an end user or application, leaving the reference file in the file storage;

performing update operations on the check-out copy; and

performing a check-in operation by receiving the updated check-out copy from the end user or application and backing up the checked-in file when updating the Datalink data type.

7. A method as defined in claim 5, wherein the step of performing automatic backup comprises the steps of:

identifying the updated change data with respect to the reference file as a delta file of changes;

determining if the updated change data delta file is smaller in size than the updated file copy by greater than a threshold value relative to the updated file; and

maintaining the delta file at the backup server when the difference in size is less than the threshold value, and maintaining an unencoded version file at the backup server when the size is greater than the threshold value.

8. A method as defined in claim 7, wherein the updated change data comprises a delta compression file of compressed changes.

9. A method as defined in claim 5, wherein the step of performing automatic backup comprises the steps of:

identifying the updated change data as a delta file of changes;

performing delta compression on the updated change data to reduce the size of the updated change data;

determining if the compressed updated change data is smaller in size than the updated file copy by greater than a threshold value relative to the updated file; and

maintaining the delta file at the backup server when the difference in size is less than the threshold value and maintaining an unencoded version file at the backup server when the size is greater than the threshold value.

2. A method of appending data to a file maintained in file storage by a file manager and referentially linked from a database management system (DBMS), the method comprising the steps of:

linking the reference file to the DBMS with a Datalink data type;

permitting read-only access to the reference file through the file manager;

performing file append operations that add updated change data to the end of the reference file to define an appended file;

permitting continuous availability of the reference file to system users during the file append operations by continuously maintaining the link to the reference file during the file append operations;

updating the Datalink data type at the DBMS to refer to the appended data as a single transaction; and

performing automatic backup of the appended file by providing a copy of the reference file and appended data to a backup server.

3. A method as defined in claim 2, wherein the step of performing automatic backup comprises the steps of:

identifying the appended data; and

maintaining a copy of the reference linked file and successive appended changes to the reference file copy at the backup server.

4. A method as defined in claim 3, wherein the appended changes comprise a delta compression file of compressed changes.

10. A method as defined in claim 2, wherein the step of performing automatic backup comprises associating successive file versions of data with corresponding successive non-null values of a Datalinks data type column.

11. A computer system comprising:

a file server that has a file management system and is connected to end users or applications that comprise file server clients;

a client system that supports file modification operations to copies of stored files;

a file manager that executes in the file server and referentially links the stored files from a database management system (DBMS) with a Datalink data type, recognized by the DBMS, that identifies a file linked with the Datalinks data type as permitting read-only access, wherein the file manager permits file modification operations on the linked file such that the modifications are performed on a copy of the linked file and the stored file is continuously available to computer system users during the file modification operations by continuously maintaining the link to the stored file during the file modification operations and by updating the link to refer to the modified copy of the linked file as a single transaction.

12. A computer system as defined in claim 11, wherein the file manager further permits updating the file in file storage by transactionally unlinking the file referenced from the DBMS with the Datalink data type and linking the updated file and performing a transactional automatic backup operation on the updated file by providing a file copy to a backup server.

13. A computer system as defined in claim 12, wherein the file modifications comprise file append operations.

14. A computer system as defined in claim 13, wherein the file manager performs the automatic backup by identifying the appended data and by maintaining a copy of the reference stored file and successive appended changes to the copy at the backup server.

15. A computer system as defined in claim 13, wherein the appended changes comprise a delta compression file of compressed changes.

16. A computer system as defined in claim 13, wherein the file manager performs the automatic backup by identifying the appended data and by maintaining a copy of the reference stored file and successive appended changes to the copy at the backup server.

17. A computer system as defined in claim 12, wherein the file modifications comprise file update operations.

18. A computer system as defined in claim 17, wherein the file manager permits the file update operations by first performing a check-out operation by creating a check-out copy of the reference stored file, leaving the reference stored file in the file storage, then permitting the update operations to be performed on the check-out copy, and then performs a check-in operation by receiving the updated check-out copy and using it as the backup file copy.

19. A computer system as defined in claim 17, wherein the file manager performs the automatic backup by identifying the updated change data with respect to the reference stored file, determining if the updated change data is smaller in size than an unencoded versions file by greater than a threshold value relative to the unencoded versions file, and backing up the delta file when the difference in size is less than the threshold value and the unencoded version file when the size is greater than the threshold value.

20. A computer system as defined in claim 19, wherein the updated change data comprises a delta compression file of compressed changes.

21. A computer system as defined in claim 17, wherein the file manager performs the automatic backup by identifying the updated change data, performing data compression on the updated change data to reduce the size of the updated change data, determining if the compressed updated change data is smaller in size than an unencoded versions file by greater than a threshold value relative to the unencoded versions file, and backing up the delta file when the difference in size is less than the threshold value and the unencoded version file when the size is greater than the threshold value.

22. A file server comprising:

a processor;

file storage in which data files are maintained and accessed by a file management system that supports modifications to the files;

a database management system (DBMS) that referentially links the data files at the file manager from the DBMS with a Datalink data type, recognized by the DBMS; and

a file management system, having a file manager, in which the linked files are given read-only access and the file manager permits file modification operations on a linked file such that the modifications are performed on a copy of the linked file and the file in file storage is continuously available to computer system users during the file modification operations by continuously maintaining the link to the file in file storage during the file modification operations and by updating the link to refer to the modified copy of the linked file as a single transaction.

23. A file server as defined in claim 22, wherein the file manager further permits updating the file in file storage by transactionally unlinking the old file version referenced from the DBMS with the Datalink data type, linking the updated file version and performing a transactional automatic backup operation on the updated file by providing a file copy to a backup server.

24. A file server as defined in claim 23., wherein the file modifications comprise file append operations.

25. A file server as defined in claim 24, wherein the file manager performs the automatic backup by identifying the appended data and by maintaining a copy of the referenced base file and successive appended changes to the copy at the backup server.

26. A file server as defined in claim 24, wherein the appended changes comprise a delta compression file of compressed changes.

27. A file server as defined in claim 24, wherein the file manager performs the automatic backup by identifying the appended data and by maintaining a copy of the referenced base file and successive appended changes to the copy at the backup server.

28. A file server as defined in claim 23, wherein the file modifications comprise file update operations.

29. A file server as defined in claim 28, wherein the file manager permits the file update operations by first performing a check-out operation by creating a check-out copy of the referenced base file, leaving the referenced base file in the file storage, then permitting the update operations to be performed on the check-out copy, and then performs a check-in operation by receiving the updated check-out copy and using it as the backup file copy.

30. A file server as defined in claim 28, wherein the file manager performs the automatic backup by identifying the updated change data with respect to the referenced base file, determining if the updated change data is smaller in size than the referenced base file by greater than a threshold value relative to the base file, and maintaining a copy of the referenced base file and the updated change data if the difference in size is greater than the threshold value.

31. A file server as defined in claim 30, wherein the updated change data comprises a delta compression file of compressed changes.

32. A file server as defined in claim 28, wherein the file manager performs the automatic backup by identifying the updated change data, performing data compression on the updated change data to reduce the size of the updated change data, determining if the compressed updated change data is smaller in size than the referenced base file by greater than a threshold value relative to the referenced base file, and maintaining a copy of the referenced base file and the compressed updated change data if the difference in size is greater than the threshold value.

33. A program product data storage device, tangibly embodying a program of machine-readable instructions executable by a computer system, the program product comprising:

a recordable media; and

instruction steps recorded on the recordable media, the instruction steps comprising a file manager when executed by the computer system that accesses files maintained in file storage and communicates with a database management system (DBMS) that supports the linking of external files, wherein the file manager referentially links the files from the DBMS with a Datalink data type, recognized by the DBMS, that identifies a file linked with the Datalink data type as permitting read-only access, and the file manager permits file modification operations on a linked file such that the modifications are performed on a copy of the linked file and the file in file storage is continuously available to computer system users during the file modification operations by continuously maintaining the link to the file in file storage during the file modification operations and by updating the link to refer to the modified copy of the linked file as a single transaction.

34. A program product as defined in claim 33, wherein the file manager further permits updating the file in file storage by transactionally unlinking an old version of the file and linking an updated version of the file from the DBMS and performing a transactional automatic backup operation on the updated file by providing a copy of the updated version to a backup server.

35. A program product as defined in claim 34, wherein the file modifications comprise file append operations.

36. A program product as defined in claim 35, wherein the file manager performs the automatic backup by identifying the appended data and by maintaining a copy of the referenced base file and successive appended changes to the copy at the backup server.

37. A program product as defined in claim 35, wherein the appended changes comprise a delta compression file of compressed changes.

38. A program product as defined in claim 34, wherein the file modifications comprise file update operations.

39. A program product as defined in claim 38, wherein the file manager permits the file update operations by first performing a check-out operation by creating a check-out copy of the referenced base file, leaving the base file in the file storage, then permitting the update operations to be performed on the check-out copy, and then performs a check-in operation by receiving the updated check-out copy and using it as the backup file copy.

40. A program product as defined in claim 39, wherein the file manager performs the automatic backup by identifying the updated change data, performing data compression on the updated change data to reduce the size of the updated change data, determining if the compressed updated change data is smaller in size than the referenced base file by greater than a threshold value relative to the referenced base file, and maintaining a copy of the base file and the compressed updated change data if the difference in size is greater than the threshold value.

41. A program product as defined in claim 38, wherein the file manager performs the automatic backup by identifying the updated change data with respect to the referenced base file, determining if the updated change data is smaller in size than the referenced base file by greater than a threshold value relative to the referenced base file, and maintaining a copy of the referenced base file and the updated change data if the difference in size is greater than the threshold value.

42. A program product as defined in claim 41, wherein the updated change data comprises a delta compression file of compressed changes.