Data recovery in a distributed system

• US 20030065685A1
• Filed: 07/24/2002
• Published: 04/03/2003
• Est. Priority Date: 01/28/2000
• Status: Active Grant

• Current Assignee: Nokia Solutions and Networks US LLC (Nokia Corporation)
• Original Assignee: Nokia Solutions and Networks US LLC (Nokia Corporation)
• Inventors: Belcaid, Adel, Lahdensuo, Kari
• Granted Patent: US 7,231,408 B2
• Time in Patent Office: Days
• US Class Current: 707/200
• CPC Class Codes: G06F 11/1658 Data re-synchronization of a redundant component, or initial sync of replacement, additional or spare unit
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 11/2048 where the redundant components share neither address space nor persistent storage
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 2201/80 Database-specific techniques
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

In a distributed system where data is maintained in at least two databases and the data comprises at least one data element, the amount of data transmitted during data recovery is minimized by comparing (210) a first total of the data element of the data in a first database with a second total of a corresponding data element of corresponding data in a second database. An updating procedure for the data element is initiated (213, 214) if the first total and the second total are not the same.

Claims

1. A method of recovering data in a system where the data is maintained in at least two databases and the data comprises at least one data element, the method comprising:

initiating recovery of the data;

calculating a first total from the data element of the data in a first database and a second total from a corresponding data element of corresponding data in a second database;

comparing the first total with the second total; and

initiating an updating procedure for the data element if the first total and the second total are not the same.

2. The method of claim 1, further comprising, if the first and second totals are not the same:

comparing the first age indication of the data element in the first database with a second age indication of the corresponding data element in the second database;

deducing on the basis of this comparison whether the data element should be updated in the first database or in the second database.

3. The method of claim 1, wherein said comparison of the first total with the second total further comprises:

forming in the first database a summary comprising at least an identifier and the first total of the data element;

sending the summary to a second database; and

performing the comparison between the first and second totals in the second database.

4. The method of claim 3, wherein the summary further comprises a first age indication indicating the age of the data element in the first database;

and the method further comprises;

comparing the first age indication with a second age indication of the corresponding data element in the second database if the first total and the second total are not the same, the second age indication indicating the age of the corresponding data element in the second database; and

deducing in the second database on the basis of this comparison whether the data element should be updated in the first database or in the second database.

5. The method of claim 4, further comprising:

starting to update the data element from the second database to the first database if the data element should be updated in the first database;

or

sending from the second database to the first database an update indication indicating the data element which should be updated in the second database.

6. The method of claim 3, wherein the first database is a master database of the data and the second database is a slave database of the data.

7. The method of claim 1 further comprising:

calculating a third total from the data in the first database and a fourth total from the corresponding data in the second database when the recovery of the data is initiated;

comparing the third total with the fourth total;

if the third total and the fourth total are the same, ending the recovery of the data;

if the third total and the fourth total are not the same, continuing the method from the step of calculating the first and second totals.

8. The method of claim 7, further comprising, if the third total and the fourth total are not the same:

a) dividing the data and the corresponding data into at least two smaller data groups according to a predetermined rule;

b) calculating for each data group a fifth total in the first database and for each corresponding data group a sixth total in the second database;

c) comparing for each data group the fifth total with the sixth total;

d) deducing on the basis of this comparison in which data group or data groups updating is needed; and

e) continuing the method from the step of calculating, for each data group needing update, the first total of the data element in the data group with the second total of the corresponding data element in the corresponding data group.

9. The method of claim 8, further comprising:

f) dividing according to a predetermined rule each data group in the first database needing update and corresponding data group in the second database into at least two smaller data groups;

g) repeating b), c) and d);

h) repeating f) and g) a predetermined number of times; and

i) continuing the method from e).

10. The method of claim 1, wherein the total is a checksum.

11. A method of recovering data in a system where the data is maintained in at least two databases and the data comprises at least one data element, the method comprising:

initiating recovery of the data;

calculating a first total from the data in a first database and a second total from corresponding data in a second database;

comparing the first total with the second total;

if the first total and the second total are the same, ending the recovery of the data;

if the first total and the second total are not the same, comparing an age indicator of a data element of the data in the first database with an age indicator of a corresponding data element of the corresponding data in the second database; and

initiating an updating procedure for the data element if the age indicators are not the same.

12. A system comprising at least two network nodescomprising a database having at least first data, the first data comprising at least one data element, the network nodes being arranged to maintain the first data;

the system being arranged to initiate recovery of the first data, to calculate during the recovery of the first data, a first total from the data element in a first database and a second total from the corresponding data element in a second database, to compare the first total with the second total and to initiate an updating procedure if the first total and second total are not the same.

13. The system of claim 12, being further arranged to compare a first age indication of the data element in the first database with a second age indication of the corresponding data element in the second database if the first total and second total are not the same, and to deduce on the basis of this comparison whether the data element should be updated in the first database or in the second database.

14. The system of claim 12 wherein, in response to the initiation of the recovery of the first data, the system is further arranged to calculate a third total from the first data in the first database and a fourth total from the corresponding first data in the second database, and to compare the third total with the fourth total, and to perform the calculation and comparison of the first and second totals only if the third total and the fourth total are not the same.

15. The system of claim 12, wherein, in response to the recovery of the first data, a first network node comprising the first database is arranged to form a summary comprising for the data element of the first data in the first database at least an identifier and a first total of the data element, and to send the summary to a second network node comprising the second database;

and

the second network node is arranged to perform said calculation of the second totals, said comparison between the first and second totals and said initiation of the updating procedure.

16. The system of claim 15, wherein the summary further comprises a first age indication indicating the age of the data element;

and

the second network node is arranged to compare the first age indication with a second age indication of the corresponding data element in the second database if the first total and second total are not the same, and to deduce on the basis of this comparison whether the data element should be updated in the first database or in the second database.

17. The system of claim 16, wherein the second network node is arranged to start to update the data element from the second database to the first database if the data element should be updated in the first database.

18. A network node comprising

a memory having at least first data, the first data comprising at least one data element;

the network node being arranged to maintain the first data and to be in connection with a second network node comprising second data corresponding to the first data;

to calculate, in response to receiving a second total of a data element in the second data, a first total of the corresponding data element in the first data, to compare the second total with the first total and to initiate an updating procedure if the first total and second totals are not the same.

19. The network node of claim 18, further being arranged to calculate, in response to receiving a third total of the second data, a fourth total from the first data, to compare the third total with the fourth total and to send the comparison result to the second network node.

20. A network node in a system where at least first data is maintained in two network nodes;

the network node comprising a memory having at least the first data, the first data comprising at least one data element;

the network node being arranged to maintain the first data and to be in connection with a second network node,

to calculate, during recovery of the first data, the network node is arranged, a first total of the data element in the first data and to send the first total to the second network node which compares the first total with a second total of the corresponding data element maintained in an other network node.

21. The network node of claim 20, further being arranged to calculate, in response to initiation of the recovery of the first data, a third total of the first data and to send the third total to the second network node which compares the third total with a fourth total of the corresponding first data maintained in the other network node, to receive a comparison result from the second network node, and only if the comparison result indicates that the third total and the fourth total are not the same to calculate and send the first total of the data element to the second network node.

22. A method of recovering data in a system where the data is maintained in at least two databases and the data comprises at least one data element, the method comprising:

initiating recovery of the data;

calculating a first total from the data element of the data in a first database and a second total from a corresponding data element of corresponding data in a second database;

comparing the first total with the second total; and

initiating an updating procedure for the data element if the first total and the second total are not the same, the updating procedure comprising;

a) dividing the data and the corresponding data into at least two smaller data groups according to a predetermined rule;

b) calculating for each data group a third total in the first database and for each corresponding data group a fourth total in the second database;

c) comparing for each data group the third total with the fourth total;

d) deducing on the basis of this comparison in which data group or data groups updating is needed; and

e) starting to update the data group or data groups in which updating is needed.

23. A method of recovering data in a system where the data is maintained in at least two databases and the data comprises at least one data element, the method comprising:

initiating recovery of the data;

calculating a first total from the data element of the data in a first database and a second total from a corresponding data element of corresponding data in a second database;

comparing the first total with the second total; and

initiating an updating procedure for the data element if the first total and the second total are not the same, the updating procedure comprising;

a) dividing the data and the corresponding data into at least two smaller data groups according to a predetermined rule;

b) calculating for each data group a third total in the first database and for each corresponding data group a fourth total in the second database;

c) comparing for each data group the third total with the fourth total;

d) deducing on the basis of this comparison in which data group or data groups updating is needed;

e) dividing according to a predetermined rule each data group in the first database needing update and corresponding data group in the second database into at least two smaller data groups;

f) repeating steps b), c) and d);

g) repeating steps e) and f) a predetermined number of times; and

h) starting to update the data group or data groups in which updating is needed.