Apparatus and method for identifying and recovering from database errors

• US 6,065,017 A
• Filed: 12/31/1997
• Issued: 05/16/2000
• Est. Priority Date: 12/31/1997
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Novell Incorporated (Open Text Corporation)
• Inventors: Barker, Kent D.
• Primary Examiner(s): Alam, Hosain T.
• Application Number:
  US09/002,283
• Time in Patent Office: 867 Days
• Field of Search: 707/8, 707/10, 707/9, 707/200-204, 709/220, 714/1, 714/2, 714/15
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1402 Saving, restoring, recovering or retrying
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A database recovery system and method that associates integrity states with predetermined database elements, each representing one or more conditions of a characteristic of interest of the associated database elements. The system repairs or replaces the database elements having associated integrity states that are less preferred so as to improve their condition and advance their associated integrity state to a more preferred integrity state. The database elements are preferably user-selected, and may be any physical or logical portion of the database, such as data records, partitions and replicas. In an hierarchically-arranged object-oriented database, the database elements may be, for example, objects, attributes or properties of objects as well as data. The database recovery system automatically repairs database elements, preferably using available processes and tools, to advance the associated integrity state from a less-preferred to a more-preferred integrity state. The database recovery system includes a state identification unit for determining the conditions of each of the database elements, and to set the associated integrity state accordingly, and an element recovery unit for improving the conditions of the database elements so as to advance the plurality of associated integrity states to a more preferred integrity state. Preferably, the characteristic may be database element validity, and the conditions include whether the database elements have been damaged or repaired. The recovery processes include an external repair tool configured to repair damaged database elements; and replacement processes such as backup retrieval processes and replica synchronization processes, for replacing particular database elements having an associated first integrity state with a copy of the particular database elements having associated second integrity state, wherein the second integrity state is a more preferred integrity state than the first integrity state.

Claims

1. A database recovery system for repairing a database, the database containing a plurality of user-defined database elements and a plurality of integrity states, each associated with one of the database elements, each of the plurality of integrity states representing a predetermined one or more conditions related to a characteristic of the associated database element, the database recovery system comprising:

a state identification unit constructed and arranged to determine the one or more conditions of each of the database elements, and to set the associated integrity state accordingly;

an element recovery unit constructed and arranged to improve said one or more conditions of the database elements so as to advance said plurality of associated integrity states to a more preferred integrity state;

and a memory, accessible by said state identification unit and said element recovery unit, constructed and arranged to store the plurality of associated integrity states) wherein said plurality of integrity states includes at least one of;

a valid state indicating said associated database element has not been damaged;

a repaired state indicating said associated database element was damaged and subsequently repaired; and

a damaged state indicating said associated database element is damaged.

2. The system of claim 1 wherein said plurality of integrity states further comprises;

an obsolete state indicating said associated database element has not been updated for a predetermined period of time.

3. The system of claim 1 wherein each of said plurality of associated integrity states is represented by a plurality of flags, each said of said plurality of flags representing an integrity state value.

4. The system of claim 1, wherein the database is a replica of a database distributed across a plurality of nodes of a network.

5. The system of claim 4, wherein said distributed database is a global directory containing information relating to objects in the network.

6. The system of claim 1, wherein said plurality of database elements comprise predetermined logical portions of the database.

7. The system of claim 1, wherein said characteristic is database element validity, and further wherein said one or more conditions includes whether said database elements have been damaged or repaired.

8. The system of claim 1, wherein said characteristic is database element age of the database element, and further wherein said one or more conditions includes the time said database element has been updated.

9. The system of claim 1, wherein said characteristic is a source of the database element.

10. A database recovery system for repairing a database having a plurality of user-defined database elements, comprising:

a plurality of integrity states, each of said plurality of integrity states representing a predetermined one or more conditions of predetermined characteristics of an associated database element;

a state identification unit configured to identify which of said associated integrity states represents a current state of said one or more conditions; and

an element recovery unit configured to apply processes to change said one or more conditions of each of said plurality of database elements and to advance said associated integrity state from a less preferred integrity state to a more preferred integrity state, wherein said plurality of integrity states includes at least one of;

a valid state indicating said associated database element has not been damaged;

a repaired state indicating said associated database element was damaged and subsequently repaired; and

a damaged state indicating said associated database element is damaged.

11. The system of claim 10, wherein said characteristic is database element validity, and wherein said state identification unit comprises:

a validation processor configured to apply validation processes to the database so as to determine the validity of the plurality of database elements; and

a first marking engine constructed and arranged to modify said plurality of associated integrity states to reflect results of said validation processes.

12. The system of claim 11, wherein said validation processes comprise external validation tools.

13. The system of claim 12, wherein said validation processes further comprise resident validation processes configured to perform database element dependency analysis of said plurality of database elements.

14. The system of claim 12, wherein said first marking engine resides in said external validation tool.

15. The system of claim 10, wherein said element recovery unit comprises:

at least one recovery process configured to change the predetermined one or more conditions so as to advance each of said plurality of integrity states from a less preferred integrity state to a more preferred integrity state; and

a second marking engine configured to modify said plurality of integrity states to reflect results of said at least one recovery.

16. The system of claim 15, wherein said recovery processes comprise:

an external repair tool configured to repair damaged database elements; and

replacement processes configured to replace particular database elements having an associated first integrity state with a copy of said particular database elements having an associated second integrity state, wherein said second integrity state is a more preferred integrity state than said first integrity state.

17. The system of claim 16, wherein said replacement processes comprise:

backup retrieval processes.

18. The system of claim 16 wherein the database is a replicated database and wherein said replacement processes comprise:

replica synchronization processes adapted to replace particular database elements having said associated first integrity state with said copy of said particular database elements residing in a replica of the database.

19. The system of claim 16, wherein said second marking engine resides in said external repair tool.

20. A method for recovering a database including a plurality of user-defined database elements, comprising the steps of:

a) associating each of a plurality of integrity states with one of the plurality of database elements, each of said plurality of integrity states representing a predetermined one or more conditions related to a characteristic of the associated database element;

b) determining said one or more conditions of each of the database elements;

c) modifying said associated integrity states to reflect results of said step b);

d) applying recovery processes to the database to improve said one or more conditions; and

e) modifying said associated integrity states to reflect results of said step d) wherein said plurality of integrity states includes at least one of;

a valid state indicating said associated database element has not been damaged;

a repaired state indicating said associated database element was damaged and subsequently repaired; and

a damaged state indicating said associated database element is damaged.

21. The method of claim 20, wherein said characteristic is database element validity, and wherein said step b) comprises the steps of:

1) apply one or more validation processes to the database so as to determine the validity of the plurality of database elements; and

2) modifying said plurality of associated integrity states to reflect results of said step b)1).

22. The method of claim 21, wherein said step b)1) comprises the step of:

i) applying one or more external validation tools to one or more of said plurality of database elements.

23. The method of claim 22, wherein said step d)1) comprises the steps:

ii) applying an external repair tool to one or more of said plurality of database elements; and

iii) replacing particular database elements having an associated first integrity state with a copy of said particular database elements having an associated second integrity state, wherein said second integrity state is a more preferred integrity state than said first integrity state.

24. The method of claim 21, wherein said step d) comprises the steps of:

1) modifying said one or more conditions so as to advance each of said plurality of integrity states from a less preferred integrity state to a more preferred integrity state; and

2) modifying said plurality of integrity states to reflect results of said step d)1).

25. The method of claim 20, wherein said plurality of integrity states comprises:

a valid state indicating said associated database element has not been damaged;

a repaired state indicating said associated database element was damaged and repaired; and

a damaged state indicating said associated database element is damaged,

wherein said valid state is a most preferred integrity state and said damaged state is a least preferred integrity state.

26. A database recovery system that identifies database elements which have an associated integrity state that is a less preferred integrity state, said integrity state representing a predetermined one or more current conditions of a characteristic of the associated database element, said database recovery system repairing and replacing said database elements so as to advance said database elements to a more preferred integrity state wherein said plurality of integrity states includes at least one of:

a valid state indicating said associated database element has not been damaged;

a repaired state indicating said associated database element was damaged and subsequently repaired; and

a damaged state indicating said associated database element is damaged.

27. A controller for enabling a processor to recover a replica of a distributed database, the database containing a plurality of user-defined database elements and a plurality of integrity states, each associated with one of the database elements, each of the plurality of integrity states representing a predetermined one or more conditions related to a characteristic of the associated database element, the controller comprising:

a state identifier constructed and arranged to determine the one or more conditions of each of the database elements, and to set the associated integrity state accordingly; and

an element recovery mechanism constructed and arranged to improve said one or more conditions of the database elements so as to advance said plurality of associated integrity states to a more preferred integrity state wherein said plurality of integrity states includes at least one of;

a valid state indicating said associated database element has not been damaged;

a repaired state indicating said associated database element was damaged and subsequently repaired; and

a damaged state indicating said associated database element is damaged.

28. A computer program product comprising a computer readable medium having computer program logic recorded thereon for enabling a processor in a computer system wherein a database is stored, to recover from errors in the database, said computer program product adapted to cause the computer system to perform the steps of:

a) associating each of a plurality of integrity states with one of the plurality of database elements, each of said plurality of integrity states representing a predetermined one or more conditions related to a characteristic of the associated database element;

b) determining said one or more conditions of each of the database elements;

c) modifying said associated integrity states to reflect results of said step b);

d) applying recovery processes to the database elements having a less preferred integrity state to improve said one or more conditions; and

e) modifying said associated integrity states to reflect results of said step d) wherein said plurality of integrity states includes at least one of;

a valid state indicating said associated database element has not been damaged;

a repaired state indicating said associated database element was damaged and subsequently repaired and

a damaged state indicating said associated database element is damaged.