Distributed Name Service (DNS) Management Operations Manual

The Name Exporter
How DNS Exports the Name Database
5–2 31258 Tandem Computers Incorporated
TMF and the Name
Manager
The name manager is a TMF server; DNSCOM and the user applications are
requesters, regarded as clients of the name manager. The name manager receives
TMF transactions through $RECEIVE. Consequently, the NMA (or DNSCOM) has
control over TMF transactions. The DNS database is TMF-protected; therefore, each
update to the database must occur under a TMF transaction. As long as you are using
DNSCOM to update the DNS database, and TMF is up and running before starting a
DNS configuration, each update to the DNS database is automatically under a TMF
transaction.
The name manager does exert transaction control in the case where an error is detected
during a database update. If the DNS database has been partly updated by the
transaction, the name manager unilaterally aborts the transaction to guard against the
possibility that the requester ignores the error and calls ENDTRANSACTION. (This
would cause database consistency errors.)
The Name Exporter The name exporter process exports names to multiple nodes by replicating
information about names on those nodes. The name exporter process sends copies of
new database name definitions and updates of existing definitions to remote nodes.
Each active DNS configuration with the ALLOWEXPORTS attribute set to ON has a
name exporter. (There may be many per node.)
Naming the Name Exporter
to Support Exporting
The name exporter process runs with either its default name ($ZDNX) 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 exporters and the same process name specified for their name managers.
Assigning a name exporter process name is done at DNS initialization, which is
discussed under “Initializing and Starting DNS Configurations” in Section 3.
TMF and the Name
Exporter
When a name definition is exported, a TMF transaction is started by the exporter at the
exporting system. TMF participates in updating the DNS database at the importing
system. If the export transaction is successful, the exporting system updates its own
database, indicating that the name is successfully exported. If any errors occur in this
process, the transaction is aborted, thus restoring both the local and remote databases
to their prior state.
The exporter does not run as a NonStop process pair; if it fails, it is automatically
recreated by the name manager.