A replication subscription is a set of definitions that define the relationship between one or more source and target tables, the structure of a target table, and the way the Apply program replicates data to the target table: when, how often, and which enhancements. Each definition is called a member and also defines the type of target table to be created, such as a user copy table or a replica. Data is replicated from all replication source tables to all target tables in the same processing cycle, and all data is replicated from all replica target tables to the replication source table in the same processing cycle.
The replication subscription logically groups one or more definitions that are somehow related; for example, source tables that have RI constraints. For the related tables, the changed data needs to be copied to the target tables at the same time, or in the same subscription interval. See "Data Consistency Requirements" for more information about replication subscriptions and RI constraints.