You create one or more replication definitions to describe each primary (source) table.
A replication definition lists a table’s columns and datatypes, the columns that make up the primary key, the columns that can be used in subscribing to the primary data, and specifies the location of the primary version of the table.
A replication definition may include additional settings to let you customize how you will use it. For example, you can create a replication definition just for replicating into a standby database in a warm standby application.
You then create subscriptions for transactions on the data defined in the replication definition. A subscription instructs Replication Server to copy transactions for all rows or for qualifying rows only. Copies of a table can be limited to only the rows or columns needed.
Typically, creating a subscription causes Replication Server to copy the initial requested data from the primary database to the replicate database. This process is called subscription materialization. Once the subscription is created and materialized, Replication Server begins distributing database operations for the primary data as they occur.