Release 10.1B: OpenEdge Replication
User Guide


How OpenEdge Replication works

OpenEdge Replication typically occurs with activity between the Replication server on the source database on the primary machine and the Replication agent on the target database on the secondary machine. If the Replication agent loses communication contact with the Replication server, you perform failover to move all database update activity from the source database to the target database. Once the primary machine becomes available again, you can move, or fail back, all the database update activity to the primary database or machine. To minimize downtime to your application, you can schedule the failback process to run when you want.

Steps in the OpenEdge Replication process are as follows:

  1. During primary (normal) replication, the primary database has the role of source database and the secondary database has the role of target database. The Replication server exists on the source database and the Replication agent exists on the target database.
  2. If there is a failure on the machine hosting the primary database, the Replication agent on the target database loses communication contact with the source database’s Replication server.
  3. The Replication agent on the target database enters pretransition.
  4. Transition then occurs, making the secondary database (formerly a target) a source database.
  5. All database activity is failed over to the secondary database, which is now functioning as a source database. The secondary database now becomes the production database.
  6. At some point, the machine hosting the primary database is fixed.
  7. Transition is initiated, and the primary database on the repaired machine changes its role from source to target. At this point, the secondary database is the source and the primary database is the target.
  8. Secondary replication, which is essentially primary replication in reverse, is performed.
  9. At a convenient time, the failback process can be performed to return the databases to the roles originally established, with the primary database as the source and the secondary database as the target. This can be done in either of the following ways:
    • Transition the secondary database using the failover command.
    • Transition the primary database and then do a separate transition of the secondary database. (This is known as controlled transition.)

Each of these steps is described in the following sections.


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