Synchronization of plural databases in a database replication system when replication is slower than the synchronization process
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 define a loading stream. The successively sent blocks of data are posted into the target database when the replication stream is occurring slower than the loading stream. Synchronization or resynchronization thereby occurs simultaneously with replication.
1. An automated 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) sending 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, the successively sent blocks of data defining a loading stream, wherein the successive blocks of data are not the same as the changes in the source database being sent in the replication stream of step (a);
(c) ensuring that the loading stream of step (b) is ahead of the replication stream of step (a);
(d) posting the successively sent blocks of data into the target database; and
(e) applying the replication stream into the target database,
the method thereby allowing synchronization or resynchronization to occur simultaneously with replication.
2. The method of claim 1 wherein the target database and the source database are both on-line during the synchronization or resynchronization and replication.
3. The method of claim 1 wherein step (c) is performed by a loader.
4. The method of claim 1 wherein steps (b) and (c) are performed by a loader.
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 non-transitory tangible computer-readable medium holding computer-executable instructions for performing the steps of:
(a) sending 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, the successively sent blocks of data defining a loading stream, wherein the successive blocks of data are not the same as the changes in the source database being sent in the replication stream of step (a);
(c) ensuring that the loading stream of step (b) is ahead of the replication stream of step (a);
(d) posting the successively sent blocks of data into the target database; and
(e) applying the replication stream into the target database,
the method thereby allowing synchronization or resynchronization to occur simultaneously with replication.
6. 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.
7. The article of manufacture of claim 5 wherein step (c) is performed by a loader.
8. The article of manufacture of claim 5 wherein steps (b) and (c) are performed by a loader.