Understanding the Architecture of MultiSite


The following sections describe the MultiSite architecture.

Replicated Database Sets

A database set consists of a schema repository and its associated user databases. A user database cannot exist without its corresponding schema repository, so when you replicate a database set, both the schema repository and the user database are replicated. When you work with a database replica, you are working with two physical databases: a schema repository replica and a user database replica.

Clans, Families, and Sites

A clan (Figure 1) consists of all replicas of a database set. Within a clan, replicas are grouped into replica families. A replica family is all the replicas of a specific database.

Figure 1 A MultiSite Clan

Schema repositories and user databases belong to separate replica families. For user databases, the family name is the same as the database name. The family name of a schema repository is always MASTR.

A site is a named collection of replicas in the same clan that reside at the same location. Each site has a schema repository replica and at most one replica from each user database family. Each site is served by a synchronization server, which receives and sends update packets to replicas within its family. Updates for a site can contain updates to the user database replicas, the schema repository replica, or both.

Kinds of Schema Repositories

Within a clan, one of the schema repository replicas is the working schema repository. At the working schema repository, you can change schemas and create additional user databases which can then be replicated. At other schema repositories, you cannot change schemas or create user databases. A clan can have only one working schema repository.

At either kind of schema repository, you can perform the following tasks:

MultiSite Terminology

MultiSite documentation uses the following terms.

Term
Definition
Replica
A copy of a user database or a schema repository. To refer to a replica, use the site name and family name.
Family
All the replicas of a specific user database or all the replicas of a specific schema repository. The family name of a user database replica is the database name of the originating database. The family name of a schema repository is always MASTR.
Site
A schema repository replica and its user database replicas.
Clan
All the replicas of a schema repository and all the replicas of the associated user databases.
Replicas originating from the same database set use the same clan name, which is specified when the database set is activated.
Host, or synchronization server
The LAN name or IP address of the network node that handles packets for a site. This host must have the Rational Shipping Server installed on it.