SQL/MP Version Management Guide

Mixed Version Networks

Compaq NonStop™ SQL/MP Version Management Guide—429833-001

6-2

Fallback Nodes in a Network

A fallback node is a node on which SQL software has a lower version number than a

catalog, object, or program on the same node. Fallback occurs when you install an older

version of SQL on a node after you create newer version catalogs, objects, or programs

on the same node without first downgrading the user catalogs running on the same node.

Problems can occur because older version SQL software running on a given node cannot

access newer version objects, programs, or catalogs on the same node. For example,

version 1 or version 2 SQL software running on a particular node cannot access a

version 315 catalog or object residing on the same node.

When fallback occurs in a network, still more problems can result, because SQL

software running on one node cannot access any catalog or object that resides on another

node if the SQL software running on the other node has an older version than the catalog

or object on the node being accessed. This situation can result even if the version of the

catalog or object being accessed on the remote node is the same as or older than the

version of the SQL software running on the local node.

For example, suppose you are running version 315 SQL/MP software on a local node

and want to access a version 315 object or catalog on a remote node. Also suppose that

the remote node is running version 1 or version 2 SQL software. A version error occurs

in this case because the remote node cannot access newer version catalogs on that same

node. When such a situation arises, the remote node running older version software

becomes a fallback node.

Figure 6-2

illustrates two fallback nodes in a network and the problems this situation can

cause when software running on a version 315 node attempts to access objects on the

fallback nodes.

Figure 6-2. Fallback Nodes in a Network

Local Node

Running Version 315

NonStop(TM) SQL/MP

Version 315

NonStop SQL/MP

Software

Remote Node

Running Version 2

NonStop(TM) SQL (Fallback Node)

Version 315 Catalog

Version 315

Objects

Version 2

Objects

Version 2 Catalog

Error encountered.

VST012.vsd