Synchronization of plural databases in a database replication system with simultaneous synchronization and replication
A target database is synchronized with a source database and the source database is replicated to the target database in a database replication system. The source database is on-line during the synchronization. The source database is located at a first node of the system, and the target database is located at a second node of the system. Changes in the source database are replicated to the target database by sending a replication stream from the first node to the second node. Successive blocks of data are sent from the first node to the target database to synchronize or resynchronize the target database with the source database. Each block of data includes one or more rows of data. The successively sent blocks of data are inserted into the replication stream at a point when the respective blocks of data are current or consistent in the source database, and the replication stream is posted to the target database. Synchronization or resynchronization thereby occurs simultaneously with replication.
1. A method for synchronizing a target database with a source database and replicating the source database to the target database in a database replication system, wherein the source database is on-line during the synchronization, the source database being located at a first node of the system, and the target database being located at a second node of the system, the method comprising:
(a) replicating changes in the source database to the target database by sending a replication stream from the first node to the second node;
(b) sending successive blocks of data from the first node to the target database to synchronize or resynchronize the target database with the source database, each block of data including one or more rows of data;
(c) inserting the successively sent blocks of data into the replication stream at a point when the respective blocks of data are current or consistent in the source database; and
(d) posting the replication stream to the target database, the method thereby allowing synchronization or resynchronization to occur simultaneously with replication.
2. The method of claim 1 wherein a marker is assigned to each of the blocks of data and is sent to the second node, wherein step (c) further comprises inserting the successively sent blocks of data into the replication stream at a point when the marker arrives at the second node.
3. The method of claim 2 wherein the markers are sent to the second node along with their respective blocks of data.
4. The method of claim 1 wherein the target database and the source database are both on-line during the synchronization or resynchronization and replication.
5. An article of manufacture for synchronizing a target database with a source database and replicating the source database to the target database in a database replication system, wherein the source database is on-line during the synchronization, the source database being located at a first node of the system, and the target database being located at a second node of the system, the article of manufacture comprising a computer-readable medium holding computer-executable instructions for performing the steps of:
(a) replicating changes in the source database to the target database by sending a replication stream from the first node to the second node;
(b) sending successive blocks of data from the first node to the target database to synchronize or resynchronize the target database with the source database, each block of data including one or more rows of data;
(c) inserting the successively sent blocks of data into the replication stream at a point when the respective blocks of data are current or consistent in the source database; and
(d) posting the replication stream to the target database, the method thereby allowing synchronization or resynchronization to occur simultaneously with replication.
6. The article of manufacture of claim 5 wherein a marker is assigned to each of the blocks of data and is sent to the second node, wherein step (c) further comprises inserting the successively sent blocks of data into the replication stream at a point when the marker arrives at the second node.
7. The article of manufacture of claim 6 wherein the markers are sent to the second node along with their respective blocks of data.
8. The article of manufacture of claim 5 wherein the target database and the source database are both on-line during the synchronization or resynchronization and replication.