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RTR Server Types
• Concurrent servers
• Callout servers
These are described in the next few paragraphs. You specify
server types to your application in RTR API calls.
RTR server types help to provide continuous availability and a
secure transactional environment.
Standby server
The standby server remains idle while the RTR primary
backend server performs its work, accepting transactions and
updating the database. When the primary server fails, the
standby server takes over, recovers any in-progress transactions,
updates the database, and communicates with clients until
the primary server returns. There can be many instances of a
standby server. Activation of the standby server is transparent
to the user.
A typical standby configuration is shown in Figure 1–12,
Standby Server Configuration. Both physical servers running
the RTR backend software are assumed by RTR to connect
to the same database. The primary server is typically in use,
and the standby server can be either idle or used for other
applications, or data partitions, or facilities. When the primary
server becomes unavailable, the standby server takes over and
completes transactions as shown by the dashed line. Primary
server failure could be caused by server process failure or
backend (node) failure.
Standby in a
cluster
The intended and most common use of a standby server is in a
cluster environment. In a non- cluster environment, seamless
failover of standbys is not guaranteed.
Standby servers are ‘‘spare’’ servers which automatically
take over from the main backend if it fails. This takeover is
transparent to the application.
Figure 1–15 shows a simple standby configuration. The two
backend nodes are members of a cluster environment, and are
both able to access the database.
For any one key range, the main or primary server (Server)
runs on one node while the standby server (Standby) runs on
the other node. The standby server process is running, but RTR
does not pass any transactions to it. Should the primary node
fail, RTR starts passing transactions to (Standby). Note that
1–16 Introduction