Distributed type of database system, consistency managing method for the same, and a computer-readable recording medium with a program for making a computer execute each step of the method stored therein

• US 6,286,004 B1
• Filed: 12/07/1998
• Issued: 09/04/2001
• Est. Priority Date: 12/12/1997
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Yoshiura, Yukari, Yano, Takashi, Ikeda, Tetsuya, Maeda, Kaoru, Iizawa, Atsushi
• Primary Examiner(s): Black, Thomas
• Assistant Examiner(s): Coby, Frantz
• Application Number:
  US09/206,294
• Time in Patent Office: 1,002 Days
• Field of Search: 707/8, 707/204, 707/202, 707/203, 707/10, 707/24
• US Class Current: 707/615
• CPC Class Codes: G06F 16/2365 Ensuring data consistency and integrity
• 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 16/273 Asynchronous replication or reconciliation
• CPC Class Codes: Y10S 707/966 Distributed
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A distributed type of database system according to the present invention comprises a communication line for transmitting, when a transaction is generated in any of a plurality of DB sites, a request message for requesting permission of updating from the DB site to a broadcasting station site. After receiving the message, it is determined in the broadcasting station site whether a permission for updating should be given or not. The result of the determination is transmitted to all the DB sites in the broadcasting mode through a satellite.

Claims

1. A distributed type of database system comprising:

a plurality of first sites each having copied data for an arbitrary object;

a second site that is different from the first sites and that is configured to centrally manage consistency of the copied data distributed among said first sites according to management information for managing the object;

a one-to-one information transmitting unit configured to transmit, when a transaction is generated in the said first sites, updating permission request information for requiring permission of updating of the copied data for the arbitrary object stored therein from each of said first sites to said second site; and

a one-to-many information transmitting unit configured to receive the updating permission request information from said one-to-one information transmitting unit, to determine whether the request for updating is to be permitted by said second site or not according to the received updating permission request information and management information for the object, and to broadcast a result of the determination from said second site to said first sites.

2. A distributed type of database system according to claim 1, wherein:

said one-to-one information transmitting unit is a communication line connecting said second site and said first sites configured to enable transmission of the updating permission request information; and

said one-to-many information transmitting unit is a broadcasting/distributing facility configured to distribute a result of the determination from said second site to said first sites in a broadcasting mode.

3. A consistency managing method for a distributed type of database system, which database system has a plurality of first sites each having copied data for an arbitrary object therein and a second site, different from the first sites, and configured to centrally manage consistency of copied data distributed among said first sites according to management information for managing the object, said method comprising:

an updating permission requesting step of generating, when a transaction is generated in one of said first sites, updating permission request information including information after updating for at least one object for which copied information is required to be updated, and transmitting the generated updating permission request information to said second site;

an updating permission determining step of receiving the updating permission request information transmitted in the updating permission requesting step by said second site and determining whether management information for the object is allowed to be updated or not according to the received updating permission request information as well as to management information for the object;

an updating permission/inhibition information generating step of updating, when it is determined in the updating permission determining step that management information for the object is allowed to be updated, management information for the object, generating updating permission information including information for the object after updating, and also generating, when it is determined in the updating permission determining step that the management information is not allowed to be updated, updating inhibition information; and

a broadcasting/distributing step of distributing the updating permission information or updating inhibition information generated in the updating permission/inhibition information generating step from said second site to said first sites in a broadcasting mode.

4. A consistency managing method for a distributed type of database system according to claim 3, wherein:

said management information includes a latest time stamp for an object related to the copied data distributed among said first sites;

in the updating permission requesting step a time stamp for an object requesting permission for updating is set in the updating permission request information when the updating permission request information is generated; and

in the updating permission determining step it is determined whether updating is allowable or not according to a result of comparison of the time stamp set in the updating permission request information to the time stamp in the corresponding management information.

5. A consistency managing method for a distributed type of database system according to claim 3 further comprising:

a first updating step of updating corresponding copied data using information after updating stored in the site when any of said first sites receives updating permission information for transaction generated in that site itself, and updating the corresponding copied data using information after updating included in the updating permission information when any of said first sites receives updating permission information for a transaction generated in some other first site; and

a first aborting step of aborting the corresponding transaction when any of said first sites receives an updating inhibition information for a transaction generated in the site.

6. A consistency managing method for a distributed type of database system according to claim 5 further comprising:

a first updating situation determining step of determining, when, in any of said first sites, updating permission information for transaction generated in the other first site is received, as to whether at least one of the objects required to be updated in transaction generated in the site has been already been updated in transaction generated in the other first site or not according to the received updating permission information;

a second aborting step of aborting, when it is determined in the first updating situation determining step that the at least one object has been updated in association with the transaction generated in the site, according to the received updating permission information.

7. A consistency managing method for a distributed type of database system according to claim 6;

wherein, in the updating permission/inhibition generating step, when the updating permission information is generated, a point of time previously specified during or before generation of the updating permission information is set as a time stamp for an object allowed to be updated in the updating permission information as well as in the corresponding management information; and

in the first updating situation determining step, it is determined whether at least one of the objected required to be updated has already been updated or not in transaction generated in the other first site, according to a result of comparison of the time stamp of the object required to be updated in transaction generated in the site to the corresponding time stamp in the updating permission information.

8. A consistency managing method for a distributed type of database system according to claim 5, further comprising:

a second updating situation determining step of determining, when, in any of said first sites, the updating permission information is received before transmission of the updating permission request information, whether at least one of the objects required to be updated in transaction generated in the site has already been updated in the transaction generated in other first site or not according to the received updating permission information; and

a third aborting step of aborting, when it is determined in the second updating situation determining step, the corresponding transaction in the first site.

9. A consistency managing method for a distributed type of database system according to claim 8;

wherein, in the updating permission/inhibition information generating step, when the updating permission information is generated, a preset point of time during or before generation of the updating permission information is set as a time stamp for an object allowed to be updated in the updating permission information as well as in the corresponding management information, and

in the second updating situation determining step, it is determined whether at least one of the objects required to be updated has already been updated in transaction generated in other first site or according to a result of comparison of the time stamp of an object required to be updated in transaction generated in the site to the corresponding time stamp in the updated permission information.

10. A consistency managing method for a distributed type of database system according to claim 5 further comprising:

an updating situation inquiring step of inquiring, when, in the first site having executed the updating permission requiring step and transmitted the updating permission requesting information to the second site, any of the updating permission information and updating inhibition information corresponding to the transmitted updating permission requesting information can not be received, updating situation of the object required to be updated at a specified timing;

an updating situation transmitting step of generating, when an inquiry on updating situation is addressed from the first site, updating situation information according to management information for the corresponding object in the second site and transmitting the generated updating situation information only to the first site;

an updating situation determining step of determining, when the updating situation information is received, whether updating of the corresponding object has been allowed according to the received updating situation information;

a second updating step of updating, when it is determined in the updating situation determining step that updating has been allowed in the first site, the corresponding data using information after updating stored in the site; and

a fourth aborting step of aborting, when it is determined in the updating situation determining step that updating has not been allowed in the first site, the corresponding transaction.

11. A consistency managing method for a distributed type of database system according to claim 5 further comprising:

a representative site specifying step of specifying at least one first site as a representative site for storing therein the latest information of an object for copied data existing in the system;

an updated information transmitting step of transmitting, when, in the first site specified as a representative site, the corresponding data in the site is updated to the latest information, updated information including a site identification information for the site and indicating that the copied data for the object has been updated to the second site; and

a site information registering/managing information for registering site identification information included in the received updated information in a latest information storing site prepared as one of management information for the object for management.

12. A consistency managing method for a distributed type of database system according to claim 11, wherein, in the representative site specifying step:

at least one representative site for storing therein the latest information is specified from the plurality of first sites for each object for copied data existing in a system, and

site identification information for the first site specified as a representative site is registered in representative site information prepared as one of management information for the object.

13. A consistency managing method for a distributed type of database system according to claim 11 further comprising:

an updated information managing step of preserving information after updating for an object included in the updating permission requesting information when updating is allowed in the updating permission determining step, and aborting the update information for the object when the updated information is received from at least one of the representative sites.

14. A consistency managing method for a distributed type of database system according to claim 11 further comprising:

a site information distributing step of distributing the latest information storing site information at a specified timing from the second site to said first sites; and

a copying step of selecting one first site from the distributed latest information storing site information according to the necessity when the latest information storing site information is received in the first site and copying the latest information for the corresponding object from the selected first site.

15. A consistency managing method for a distributed type of database system according to claim 11 further comprising:

a site information transmitting step of identifying a first site not having transmitted the updated information from among the first sites specified as representative sites for a specified objected at a specified timing in the second site according to the representative site information as well as to the latest information storing site information and transmitting the latest information storing site information for the identified object only to the identified first site; and

a second copying step of selecting one first site from the received latest information storing site information when the latest information storing site information is received in the first site specified as a representative site, and copying the latest information for the object from the selected first site.

16. A consistency managing method for a distributed database system according to claim 11;

wherein said updating permission/inhibition information generating step further comprises a third step of setting, when generating the updating inhibition information, the latest information storing site information for the object in the updating inhibition information, further setting, when the corresponding transaction is aborted in the first, second and third aborting steps in the first site, one site from the latest information storing site information included in the updating inhibition information, and copying the last information for the corresponding object from the selected first site.

17. A consistency managing method for a distributed type of database system according to claim 11;

wherein said updating situation transmitting step further comprises a fourth copying step of setting, when generating the updating situation information, latest information storing site information for the corresponding object in the updating situation information, selecting, when the corresponding transaction is aborted in the fourth aborting step in the first site, one of the first sites from the latest information storing site included in the updating situation information, and copying the latest information for the corresponding object from the selected first site.

18. A consistency managing method for a distributed type of database system according to claim 5, further comprising:

a clock signal distributing step of generating a clock signal for unifying a clock for a system as a whole in the second site and distributing the generated clock signal to said first sites in the broadcasting mode;

wherein, in said updating permission/inhibition information generating step, a time stamp for an object having been allowed to be updated is generated using the clock signal, the generated time stamp is set in the updating permission information as well as in the management information, and in the first updating step, the time stamp in the updating permission information is set as a time stamp for the corresponding copied data.

19. A consistency managing method for a distributed type of database system according to claim 10, wherein, in said updating situation transmitting step a time stamp set in management information for the corresponding object is set in the updating situation information, and in the second updating step the time stamp in the updating situation information is set as a time stamp for the corresponding copied data.

20. A consistency managing method for a distributed type of database system according to claim 5;

wherein, in said first updating step, when the corresponding copied data is updated according to the updating permission information, the copied data is updated on the condition that preset conditions for updating are satisfied.

21. A computer-readable recording medium with a program for making a computer execute each step in the consistency managing method for a distributed type of database system according to claim 3.