Recovery of a remotely initiated distributed prepared transaction by status report from a second database to an external coordinator

Claim 3

The method of claim 1 further comprising the step of causing said second database instance to receive from said external coordinator process instructions relating to a distributed transaction that existed in said first database instance.

Claim 4

The method of claim 2 further comprising the step of causing said second database instance to respond to said instructions by inspecting said prepared transaction information to determine whether said distributed transaction was prepared when said first database instance crashed; performing an action indicated by said instructions if said distributed transaction was prepared when said first database instance crashed.

Claim 5

The method of claim 3 wherein the step of performing an action includes rolling back changes made by said distributed transaction.

Claim 6

The method of claim 3 wherein the step of performing an action includes committing changes made by said distributed transaction to said particular database.

Claim 7

The method of claim 1 wherein: at least a portion of said particular database resides on said storage device; and the step of storing prepared transaction information includes storing said prepared transaction information into said portion of said particular database.

Claim 8

The method of claim 1 further comprising the steps of: causing said second database instance to determine whether said prepared transaction information has been completely copied to said storage device; and if said prepared transaction information has not been completely copied to said storage device, then causing said second database instance to wait for said prepared transaction information to be completely copied to said storage device before performing the step of reading said prepared transaction information.

Claim 9

A computer system comprising: storage upon which is stored a database; a first database instance executing on one or more nodes; a second database instance executing on one or more nodes; an external coordinator process executing on one or more nodes, said external coordinator process assigning to said first database instance a child transaction that makes changes to said database; said first database instance crashing after preparing said child transaction; a transaction recovery mechanism that stores in said database prepared transaction information that identifies prepared transactions that existed in said first database instance; said external coordinator process requesting status information from said second database instance; and said second database instance responding to said external coordinator process by reading said prepared transaction information from said database and indicating to said external coordinator process that said child transaction was prepared.

Claim 10

A computer system comprising: storage upon which is stored a database; a first database instance executing on one or more nodes; a second database instance executing on one or more nodes; an external coordinator process executing on one or more nodes, said external coordinator process assigning to said first database instance a child transaction that makes changes to said database; said first database instance crashing after preparing said child transaction; a transaction recovery mechanism that stores in said database prepared transaction information that identifies prepared transactions that existed in said first database instance; said external coordinator process requesting status information from said second database instance; and said second database instance responding to said external coordinator process by reading said prepared transaction information from said database and indicating to said external coordinator process that said child transaction was prepared.

Claim 11

The computer system of claim 8 wherein said transaction recovery mechanism is part of said second database instance.

Claim 12

The computer system of claim 8 wherein said external coordinating process communicates to said first database instance and said second database instance through an external interface.

Claim 13

The computer system of claim 8 wherein: said transaction recovery mechanism identifies transactions that were active in said first database instance when said first database instance crashed; and said transaction recovery mechanism does not roll back any changes made by said transactions that were active until said transaction recovery mechanism stores said prepared transaction information in said database.

Claim 14

The computer system of claim 8 wherein: said second database instance determines whether said transaction recovery mechanism has completely stored said prepared transaction information in said database; and said second database instance does not respond to said external coordinator process until said transaction recovery mechanism has completely stored said prepared transaction information in said database.

Claim 15

The computer system of claim 8 wherein: said external coordinator process assigns to said first database instance a second child transaction that makes changes to said database; said first database instance crashes after preparing said second child transaction; and said external coordinator process sends a status request to said second database instance that includes a flag; if said flag has a first value, said second database instance may respond to said status request without indicating that said second child transaction was prepared; and if said flag has a second value, said second database instance responds to said status request indicating that said second child transaction was prepared.

Claim 16

The computer system of claim 13 wherein said second database instance does not respond to said status request until said transaction recovery mechanism has all of said prepared transaction information in said database.