Availability Guide for Problem Management

Planning for Disasters
Availability Guide for Problem Management–125509
8-3
Data Recovery and Integrity
The Expand subsystem extends fault-tolerant operations to networks of geographically
distributed computer systems. You can use Expand to connect Tandem NonStop systems
at different locations to form a single network in which communications paths are
constantly available, even in the event of a single line or component failure. If one path
between nodes fails, Expand automatically reroutes and (when appropriate) retransmits
messages using the next-best available path.
The NonStop Access for Networking (NSAN) product provides alternate paths to guard
against local area network (LAN) failure in client/server environments.
Most Tandem systems are delivered with a fault-tolerant configuration. It is up to you to
maintain a fault-tolerant configuration whenever you change or add hardware. When
changing the configuration, follow the guidelines described in Section 7, “Change and
Configuration Management,” of the Introduction to Nonstop Operations Management.
The Availability Guide for Change Management contains more information about
changing your configuration.
Data Recovery and Integrity
By using the NonStop Transaction Manager/MP (TM/MP) and Remote Duplicate
Database Facility (RDF) products, you can prevent loss of data and bring your
applications up quickly after a disaster.
NonStop Transaction Manager/MP (TM/MP)
NonStop TM/MP maintains database consistency during processing. The database can
reside on a single Tandem system or be distributed over multiple nodes of an Expand
network. In either case, NonStop TM/MP ensures that the database remains consistent in
the event of a program failure, a single component failure, or the total loss of
communications between nodes.
Using NonStop TM/MP, you can also perform online dumps and audit dumps to a
remote system. This allows you to maintain a copy of the database at a remote backup
site.
Data Archiving
In the event of a computer disaster, archived data might be key to the survival of your
business. To protect essential data, you first need to determine which data is fundamental
to your operation and how much of that data your company can afford to lose before its
survival is threatened. Once you have identified the essential data, you can design a plan
for backing up the data on a regular basis. Tandem provides the following tools for
backing up data: NonStop TM/MP online dumps and the BACKUP and BACKCOPY
utilities (for archiving to tape).
Backing up data is not enough; storing data in a safe place is equally important.
Consider these guidelines when storing data:
•
Store data and archive media (disks, tapes, microfiche, and so on) in a controlled
environment at a cool temperature, away from the computer room.