Collision avoidance in bidirectional database replication

An article of manufacture for avoiding collisions in a bidirectional database replication system including a plurality of nodes connected via communication media in a topology, each node including (i) a database, (ii) a table that stores indicia of initiated transactions that are ready to be committed, but are not yet committed, and (iii) a transaction transmitter, each transaction being one or more transaction steps or transaction operations, the article of manufacture comprising a computer-readable medium holding computer-executable instructions for performing a method comprising:

• (a) the transaction transmitter of an originating node sending selected transactions posted to the database of the originating node to one or more other nodes for replication at the one or more other nodes;
• (b) pausing each transaction being executed in a database of an originating node prior to a commit operation for the transaction;
• (c) entering into the table at the originating node, indicia of the initiated transactions that are ready to be committed but that are not yet committed, and assigning a ready to commit token to the transaction;
• (d) the transaction transmitter at the originating node sending the ready to commit tokens in the table of the originating node to the one or more other nodes;
• (e) determining at each of the one or more other nodes whether the database at the one or more other nodes is prepared for a commit operation for the transactions corresponding to each received ready to commit tokens, and, if so, the transaction transmitter in each of the other nodes sends back the ready to commit tokens to the respective originating node;
• and
• (f) executing the commit operation of the transaction in the database of the originating node only upon receipt from each of the other nodes in the system of the ready to commit token originally sent from the originating node for the transaction, wherein the commit operation for each transaction in the system is paused so as to allow all of the nodes in the system to prepare for the commit and thereby avoid collisions at all of the nodes in the system.

An apparatus for avoiding collisions in a bidirectional database replication system including a plurality of nodes connected via communication media in a topology, each node including (i) a database, (ii) a table that stores indicia of initiated transactions that are ready to be committed, but are not yet committed, and (iii) a transaction transmitter, each transaction being one or more transaction steps or transaction operations, the apparatus comprising:

• (a) a transaction transmitter of an originating node which sends selected transactions posted to the database of the originating node to one or more other nodes for replication at the one or more other nodes;
• (b) means for pausing each transaction being executed in a database of an originating node prior to a commit operation for the transaction;
• (c) means for entering into the table at the originating node, indicia of the initiated transactions that are ready to be committed but that are not yet committed, and assigning a ready to commit token to the transaction, the transaction transmitter at the originating node sending the ready to commit tokens in the table of the originating node to the one or more other nodes;
• (d) means for determining at each of the one or more other nodes whether the database at the one or more other nodes is prepared for a commit operation for the transactions corresponding to each received ready to commit tokens, and, if so, the transaction transmitter in each of the other nodes sends back the ready to commit tokens to the respective originating node;
• and
• (e) means for executing the commit operation of the transaction in the database of the originating node only upon receipt from each of the other nodes in the system of the ready to commit token originally sent from the originating node for the transaction, wherein the commit operation for each transaction in the system is paused so as to allow all of the nodes in the system to prepare for the commit and thereby avoid collisions at all of the nodes in the system.

A method of avoiding collisions in a bidirectional database replication system including a plurality of nodes connected via communication media in a topology, each node including (i) a database, (ii) a table that stores indicia of initiated transactions that are at one or more predesignated intermediate points in the transaction but are not yet committed, and (iii) a transaction transmitter, each transaction being one or more transaction steps or transaction operations, the method comprising:

• (a) the transaction transmitter of an originating node sending selections transactions posted to the database of the originating node to one or more other nodes for replication at the one or more other nodes;
• (b) entering into the table at the originating node, indicia of the initiated transactions that are at one or more predesignated intermediate points in the transaction but are not yet committed, and assigning a ready to sync token to the transaction at each of the predesignated intermediate points;
• (c) the transaction transmitter at the originating node sending the ready to sync tokens in the table of the originating node to the one or more other nodes;
• (d) determining at each of the one or more other nodes whether the database at the one or more other nodes is prepared to properly process the transaction up to the intermediate point associated with the respective ready to sync token, and, if so, the transaction transmitter in each of the other nodes sends back the ready to sync tokens to the respective originating node;
• and
• (e) stopping the execution of a transaction in the system if the originating node fails to receive back a ready to sync token from at least one of the other nodes in the system for any of the predesignated intermediate points, wherein the transaction continues to execute as long as all ready to sync tokens properly return to the originating node, thereby indicating that no collisions should occur at any of the nodes in the system up to the most recent intermediate point in the transaction.

An article of manufacture for avoiding collisions in a bidirectional database replication system including a plurality of nodes connected via communication media in a topology, each node including (i) a database, (ii) a table that stores indicia of initiated transactions that are at one or more predesignated intermediate points in the transaction but are not yet committed, and (iii) a transaction transmitter, each transaction being one or more transaction steps or transaction operations, the article of manufacture comprising a computer-readable medium holding computer-executable instructions for performing a method comprising:

• (a) the transaction transmitter of an originating node sending selections transactions posted to the database of the originating node to one or more other nodes for replication at the one or more other nodes;
• (b) entering into the table at the originating node, indicia of the initiated transactions that are at one or more predesignated intermediate points in the transaction but are not yet committed, and assigning a ready to sync token to the transaction at each of the predesignated intermediate points;
• (c) the transaction transmitter at the originating node sending the ready to sync tokens in the table of the originating node to the one or more other nodes;
• (d) determining at each of the one or more other nodes whether the database at the one or more other nodes is prepared to properly process the transaction up to the intermediate point associated with the respective ready to sync token, and, if so, the transaction transmitter in each of the other nodes sends back the ready to sync tokens to the respective originating node;
• and
• (e) stopping the execution of a transaction in the system if the originating node fails to receive back a ready to sync token from at least one of the other nodes in the system for any of the predesignated intermediate points, wherein the transaction continues to execute as long as all ready to sync tokens properly return to the originating node, thereby indicating that no collisions should occur at any of the nodes in the system up to the most recent intermediate point in the transaction.

An apparatus for avoiding collisions in a bidirectional database replication system including a plurality of nodes connected via communication media in a topology, each node including (i) a database, (ii) a table that stores indicia of initiated transactions that are at one or more predesignated intermediate points in the transaction but are not yet committed, and (iii) a transaction transmitter, each transaction being one or more transaction steps or transaction operations, the apparatus comprising:

• (a) a transaction transmitter of an originating node which sends selected transactions posted to the database of the originating node to one or more other nodes for replication at the one or more other nodes;
• (b) means for entering into the table at the originating node, indicia of the initiated transactions that are at one or more predesignated intermediate points in the transaction but are not yet committed, and assigning a ready to sync token to the transaction at each of the predesignated intermediate points, the transaction transmitter at the originating node sending the ready to sync tokens in the table of the originating node to the one or more other nodes;
• (c) means for determining at each of the one or more other nodes whether the database at the one or more other nodes is prepared to properly process the transaction up to the intermediate point associated with the respective ready to sync token, and, if so, the transaction transmitter in each of the other nodes sends back the ready to sync tokens to the respective originating node;
• and
• (d) means for stopping the execution of a transaction in the system if the originating node fails to receive back a ready to sync token from at least one of the other nodes in the system for any of the predesignated intermediate points, wherein the transaction continues to execute as long as all ready to sync tokens properly return to the originating node, thereby indicating that no collisions should occur at any of the nodes in the system up to the most recent intermediate point in the transaction.

A method of replicating data in a database replication system including a source database and a target database, each transaction being one or more transaction steps or transaction operations, the method comprising:

• (a) sending to the target database any transaction steps or operations that are received and posted at the source database, the transaction steps or operations that are received and posted at the source database thereby being replicated to the target database;
• (b) pausing each transaction being executed in the source database prior to a commit operation for the transaction,
• (c) assigning a ready to commit token to the transaction;
• (d) sending the ready to commit token to the target database only after all transaction steps or operations prior to the commit operation for the transaction have been posted to the source database;
• (e) determining whether the target database is prepared for a commit operation for the transaction corresponding to the ready to commit token, and, if so, sending back the ready to commit token to the source database;
• and
• (f) executing a commit operation at the source database for a transaction only upon receipt from the target database of the ready to commit token originally sent from the source database for the respective transaction, wherein the commit operation for each transaction in the system is paused so as to allow the source and the target database to prepare for the commit.

An apparatus for replicating data in a database replication system including a source database and a target database, each transaction being one or more transaction steps or transaction operations, the apparatus comprising:

• (a) means for sending to the target database any transaction steps or operations that are received and posted at the source database, the transaction steps or operations that are received and posted at the source database thereby being replicated to the target database;
• (b) means for pausing each transaction being executed in the source database prior to a commit operation for the transaction;
• (c) means for assigning a ready to commit token to the transaction;
• (d) means for sending the ready to commit token to the target database;
• (e) means for determining whether the target database is prepared for a commit operation for the transaction corresponding to the ready to commit token, and, if so, sending back the ready to commit token to the source database;
• and
• (f) means for executing a commit operation at the source database for a transaction only upon receipt from the target database of the ready to commit token originally sent from the source database for the respective transaction, wherein the commit operation for each transaction in the system is paused so as to allow the source and the target database to prepare for the commit.