Distributed Name Service (DNS) Management Operations Manual

5 How DNS Exports the Name
Database
31258 Tandem Computers Incorporated 5–1
Exporting name definitions involves the local name manager and name exporter, and
the name managers on another system. The local name manager and name exporter
communicate through the Guardian 90 file system. The name exporter acts as the
requester, and the name manager acts as the server. In addition to this interprocessor
communications (IPC) interface, the two processes communicate through a file called
the queue file.
This section describes how the name manager, name exporter, and other DNS
elements replicate the DNS database. This replication of names from one node to
another (and the propagation of changes to replicated names) is called name
exporting. Exporting the DNS database implies at least partial replication of name
definitions and attributes at different locations.
Distribution of the DNS database usually involves a network control node (NCN). It
manages objects on one or more other nodes. Each NCN has a domain of nodes that
falls under its control. However, the power and effect of an NCN depends on the role
you assign it. Thus, you can define more than one node in a network to be an NCN.
Defining NCNs is discussed later in this section under “Distribution Strategy of
Network Control Nodes.”
The node where a name is first defined and where the definition resides is the
definition node. A name definition can only be updated or deleted by the name
manager running at the name’s definition node. Every name has one definition node.
When a name definition is replicated, the definition node is the exporting node. All
nodes listed in a name’s domain are importing nodes, nodes that receive replicated
definitions.
The Name Manager Each network node with DNS installed has a DNS name manager that manages I/O
operations against the local DNS database. The DNS name manager controls access to
the DNS name database, maintains the database files, and receives information
replicated from other nodes. Each active (running) DNS configuration has a name
manager. The name manager is a multi-threaded, NonStop process that accepts SPI
(Subsystem Programmatic Interface) requests from network management applications
(NMAs).
Naming the Name Manager
to Support Exporting
The name manager process runs with either its default name ($ZDNS) or with a user-
defined name. If a configuration on one node is to export to a configuration on
another node, the two configurations must have the same process name specified for
their name managers and the same process name specified for their name exporters.
Assigning a name manager process name is done at DNS initialization, which is
discussed under “Initializing and Starting DNS Configurations” in Section 3.