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

• US 20060212465A1
• Filed: 03/18/2005
• Published: 09/21/2006
• Est. Priority Date: 03/18/2005
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Fish, Eric Ian, Pearson, George Allen, Rathbun, Timothy Lee, Shepherd, Joel, Corbin, Scott Roger
• Granted Patent: US 7,788,225 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 readable medium including executable instructions to compare databases, comprising executable instructions 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;

allow a latency period after said first time in which changes are made to said first database and said second database; and

determine after said latency period whether said segment of said first database is in synchronization with said corresponding segment of said second database.

2. The 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 readable medium of claim 2 wherein said executable instructions to identify include executable instructions to establish a 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 readable medium of claim 1 wherein said executable instructions to identify include executable instructions to identify key data and non-key data, wherein said executable instructions include executable instructions to perform a hash on said non-key data to create hash data.

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

6. The computer readable medium of claim 4 further comprising executable instructions to compare key data from said first database to key data from said second database and hash data from said first database to hash data from said second database to identify said conditionally out of synchronization state.

7. The 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.

8. The 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.

9. The computer readable medium of claim 1 wherein said executable instructions to identify include executable instructions to identify a batch of rows of said first database, compress said batch of rows, identify non-key data and key data including a begin key value and an end key value, perform a hash on said non-key data to create hash data, and to transmit said begin key value, said end key value and said hash data to a target.

10. The computer readable medium of claim 9 further comprising executable instructions to process said begin key value, said end key value and said hash data to identify a corresponding segment within said second database, and perform a hash of said corresponding segment to produce second hash data, and determine a bad batch when said hash data does not correspond to said second hash data

11. The computer readable medium of claim 10 further comprising executable instructions to use said begin key value and said end key value to identify within said first database and said second database the set of rows corresponding to said bad batch.

12. The computer readable medium of claim 11 further comprising executable instructions to compare individual rows of said set of rows to identify rows that are conditionally out of synchronization.

13. The computer readable medium of claim 1 further comprising, executable instructions to determine when said segment of said first database is not in synchronization with said corresponding segment of said second database, and executable instructions to re-synchronize said segment of said first database with said corresponding segment of said second database during dynamic operation of said first database and said second database.

14. The computer readable medium of claim 13 wherein re-synchronizing includes executable instructions to:

retrieve values from said segment of said first database;

lock said segment; and

store said values in a marker table associated with said first database.

15. The computer readable medium of claim 14 further comprising executable instructions to:

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

16. The computer readable medium of claim 15 further comprising executable instructions to:

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

17. The computer readable medium of claim 13 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.

18. The computer readable medium of claim 17 wherein said executable instructions to re-synchronize include executable instructions to determine data directional flow.

19. The computer readable medium of claim 13 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.

20. The computer readable medium of claim 13 wherein said executable instructions to re-synchronize include executable instructions to re-synchronize using replication markers.

21. The computer readable medium of claim 13 wherein said executable instructions to re-synchronize include executable instructions to re-synchronize using a source row update technique.