Apparatus and method for identifying asynchronous data in redundant data stores and for re-synchronizing same

• US 7,788,225 B2
• Filed: 03/18/2005
• Issued: 08/31/2010
• Est. Priority Date: 03/18/2005
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Pearson, George Allen, Rathbun, Timothy Lee, Shepherd, Joel, Corbin, Scott Roger, Fish, Eric Ian
• Primary Examiner(s): Pham; Hung Q
• Assistant Examiner(s): CHEUNG, HUBERT G
• Application Number:
  US11/084,855
• Publication Number:
  US 20060212465A1
• Time in Patent Office: 1,992 Days
• Field of Search: 707/624
• US Class Current: 707/624
• CPC Class Codes: G06F 11/1662 the resynchronized component or unit being a persistent storage device re-synchronization of failed mirror storage G06F11/2082; rebuild or reconstruction of parity RAID storage G06F11/1008
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 16/273 Asynchronous replication or reconciliation

Abstract

A computer readable medium includes executable instruction to compare databases. The executable instructions are configured to identify when a segment of a first database is conditionally out of synchronization with a corresponding segment of a second database to establish a conditionally out of synchronization state at a first time. Executable instructions allow a latency period after the first time in which changes are made to the first database and the second database. Executable instructions also determine after the latency period whether the segment of the first database is in synchronization with the corresponding segment of the second database. Executable instructions also populate a resynchronization table, which is used by a replication mechanism to bring asynchronous rows into synchronization.

Claims

1. A computer storage product with a computer readable medium having computer code executed by a computer, said computer code including executable instructions to compare databases, said computer code comprising executable instructions to:

identify a segment of a first database comprising a batch of rows of said first database;

compress said batch of rows of said first database;

identify non-key data and key data in said compressed batch of rows of said first database, including a begin key value and an end key value;

perform a hash on said identified non-key data to create first hash data;

process at least said identified begin key value and said identified end key value to identify a corresponding segment of a second database;

perform a hash on at least a portion of said identified corresponding segment of said second database to create second hash data;

compare said created first hash data with said created second hash data to identify said identified segment of said first database is conditionally out of synchronization with said identified corresponding segment of said second database to establish a conditionally out of synchronization state at a first time;

allow a latency period after said first time for said first database and said second database to synchronize through existing synchronization mechanisms;

determine after said latency period that said identified segment of said first database is not in synchronization with said identified corresponding segment of said second database to form a post-latency out of synchronization state; and

re-synchronize, in response to said post-latency out of synchronization state, said identified segment of said first database with said identified corresponding segment of said second database during dynamic operation of said first database and said second database.

2. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to identify include executable instructions to establish a common format for said segment of said first database and said corresponding segment of said second database.

3. The computer storage product with said computer readable medium of claim 2 wherein said executable instructions to identify include executable instructions to establish said common format between said first database and said second database accounting for at least one of:

overlapping columns, overlapping rows, mapped data, and heterogeneous data stores.

4. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to identify include executable instructions to augment said created first hash data with user-specified non-key data.

5. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to identify include executable instructions to establish whether said segment of said first database includes rows or columns that at least partially overlap with corresponding rows or columns of said corresponding segment of said second database.

6. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to identify include executable instructions to compare sub-segments of said segment of said first database to corresponding sub-segments of said second database in parallel.

7. The computer storage product with said computer readable medium of claim 1 further comprising executable instructions to use said identified begin key value and said identified end key value to identify within said first database and said second database a set of rows corresponding said identified segment of said first database and said identified corresponding segment of said second database that are conditionally out of synchronization at said first time.

8. The computer storage product with said computer readable medium of claim 7 further comprising executable instructions to compare individual rows of said set of rows to identify rows that are conditionally out of synchronization.

9. The computer storage product with said computer readable medium of claim 1 wherein re-synchronizing includes executable instructions to:

retrieve values from said identified segment of said first database;

lock said identified segment of said first database; and

store said retrieved values from said identified segment of said first database in a marker table associated with said first database.

10. The computer storage product with said computer readable medium of claim 9 further comprising executable instructions to:

use a replication mechanism to propagate said stored retrieved values from said identified segment of said first database from said marker table to said identified corresponding segment of said second database.

11. The computer storage product with said computer readable medium of claim 10 further comprising executable instructions to:

use said replication mechanism to sequence changes to said first database.

12. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to re-synchronize include executable instructions to access an out-of-synchronization queue specifying information about out-of-synchronization database segments.

13. The computer storage product with said computer readable medium of claim 12 wherein said executable instructions to re-synchronize include executable instructions to determine data directional flow.

14. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to re-synchronize include executable instructions to re-synchronize through a direct application technique that relies upon native methods associated with either said first database or said second database.

15. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to re-synchronize include executable instructions to re-synchronize using replication markers.

16. The computer storage product with said computer readable medium of claim 1 wherein said executable instructions to re-synchronize include executable instructions to re-synchronize using a source row update technique.

17. A method, comprising:

identifying, at a computer system, a segment of a first database comprising a batch of rows of said first database;

compressing said batch of rows of said first database;

identifying non-key data and key data in said compressed batch of rows of said first database, including a begin key value and an end key value;

performing a hash on said non-key data to create first hash data;

processing at least said identified begin key value and said identified end key value to identify a corresponding segment of a second database;

performing a hash on at least a portion of said identified corresponding segment of said second database to create second hash data;

comparing said created first hash data with said created second hash data to identify said identified segment of said first database is conditionally out of synchronization with said identified corresponding segment of said second database to establish a conditionally out of synchronization state at a first time;

allowing a latency period after said first time for said first database and said second database to synchronize through existing synchronization mechanisms;

determining after said latency period that said identified segment of said first database is not in synchronization with said identified corresponding segment of said second database to form a post-latency out of synchronization state; and

re-synchronizing, in response to said post-latency out of synchronization state, said identified segment of said first database with said identified corresponding segment of said second database during dynamic operation of said first database and said second database.

18. A computer system comprising a processor and a memory in communication with said processor, said memory having therein computer code executable by said computer system, said computer code comprising executable instructions to:

identify a segment of a first database comprising a batch of rows of said first database;

compress said batch of rows of said first database;

identify non-key data and key data in said compressed batch of rows of said first database, including a begin key value and an end key value;

perform a hash on said identified non-key data to create first hash data;

process at least said identified begin key value and said identified end key value to identify a corresponding segment of a second database;

perform a hash on at least a portion of said identified corresponding segment of said second database to create second hash data;

compare said created first hash data with said created second hash data to identify said identified segment of said first database is conditionally out of synchronization with said corresponding segment of said second database to establish a conditionally out of synchronization state at a first time;

allow a latency period after said first time for said first database and said second database to synchronize through existing synchronization mechanisms;

determine after said latency period that said identified segment of said first database is not in synchronization with said identified corresponding segment of said second database to form a post-latency out of synchronization state; and

re-synchronize, in response to said post-latency out of synchronization state, said identified segment of said first database with said identified corresponding segment of said second database during dynamic operation of said first database and said second database.