Compaq Reliable Transaction Router manual Standby Server Configuration

RTR Terminology

Figure 1–12 Standby Server Configuration

TR

BE

Server

BE

Server

Primary

Server

DB

Standby

Server

Transactional shadowing

RTR Journal

LKG-11210-98WI

To increase transaction availability, transactions can be shadowed with a shadow server. This is called transactional shadowing and is accomplished by having a second location, often at a different site, where transactions are also recorded. This is illustrated in Figure 1–13. Data are recorded in two separate data stores or databases. The router knows about both backends and sends all transactions to both backends. RTR provides the server application with the necessary information to keep the two databases synchronized.

In the RTR environment, one data store (database or data file) is elected the primary, and a second data store is made the shadow. The shadow data store is a copy of the data store kept on the primary. If either data store becomes unavailable, all transactions continue to be processed and stored on the surviving data store. At the same time, RTR makes a record of (remembers) all transactions stored only on the shadow data store in the RTR journal by the shadow server. When the primary server and data store become available again, RTR replays the transactions in the journal to the primary data store through the primary server. This brings the data store back into synchronization.

Introduction 1–13