Compaq Reliable Transaction Router manual Concurrent Servers, Server1 Server2 Server3 Server4

RTR Server Types

channels within a single process or as one channel in separate processes.

Figure 1–17 Concurrent Servers

BE

Server1

Server2

Server3

Server4

A-N

LKG-11275-98WI

Callout server	The callout server provides message authentication on
	transaction requests made in a given facility, and could be used,
	for example, to provide audit trail logging. A callout server can
	run on either backend or router nodes. A callout server receives
	a copy of all messages in a facility. Because the callout server
	votes on the outcome of each transaction it receives, it can veto
	any transaction that does not pass its security checks.
	A callout server is facility based, not partition based; any
	message arriving at the facility is routed to both the server
	and the callout. A callout server is enabled when the facility is
	defined. Figure 1–18 illustrates the use of a callout server that
	authenticates every transaction (txn) in a facility.
	To authenticate any part of a transaction, the callout server must
	vote on the transaction, but does not write to the database. RTR
	does not replay a transaction that is only authenticated.

Introduction 1–19