Overview

The JADE Synchronized Database Service (SDS) environment enables you to:

Keep secondary copies of a database synchronized with a primary updating copy.
Support optional read-only access to secondary copies of the database.

An SDS environment is made up of one primary database server and one or more secondary database servers, which are usually hosted on different machines that may be in different geographic locations.

Any JADE database server node is capable of operating as the primary database server in a hot standby configuration.

Subject to licensing restrictions, a primary database server offers a passive communication port to accept connections from secondary servers and can accept multiple connections.

A secondary database server establishes a connection to its specified primary server to receive control and database tracking information. A secondary database:

Cannot be directly updated by application programs
Is modified only by the replay of audit records generated on the primary database server
Can assume the role of the primary database if the primary database becomes unavailable

You require a licence to run a Synchronized Database Environment (SDE).

JADE licenses are not transferred automatically between databases in an SDE. It is your responsibility to apply new licenses to any existing databases in an SDE. In addition, to ensure proper operation, you must apply the primary license to every secondary.

In an SDS environment, the secondary database server has a node stub that represents the primary server node. This node stub does not have the full functionality of a normal client; in particular, some statistical functions cannot be carried out on the node stub (for example, getting a node’s cache statistics). Any attempt to do so now raises exception 1265 (Environmental operation out of scope for process).

You can use the value returned by the Node class nodeRole method to distinguish the node stub from standard client nodes. For the node stub, the returned value is the Node class Role_Replay constant (as opposed to the Role_Standard constant).

For details about the database, environment, and server identities, see "Database Identities", in Chapter 3 of the JADE Database Administration Guide.