SQL/MX 2.x Installation and Management Guide (G06.24+, H06.03+)

Managing an SQL/MX Distributed Database
HP NonStop SQL/MX Installation and Management Guide—523723-004
13-15
Maintaining Local Autonomy in a Network
Table 13-3 shows that:
•
User data for CAT_1 and CAT_2 objects resides on all three nodes in the network.
•
The metadata for CAT_1 and CAT_2 resides only on node \B, where the catalogs
were created.
•
Applications that contain queries to CAT_1 and CAT_2 objects reside on all three
nodes.
•
If the node that contains a catalog’s metadata (node \B for CAT_1 and CAT_2
metadata) becomes unavailable, the surviving nodes cannot execute dynamic
queries on the catalog object data.
Note that the loss of the node where the object metadata resides does not prevent
statically-compiled queries from being performed in application processes on the
surviving nodes to access local data. However, they can query only data located on the
local node or some other surviving node.
A minor reconfiguration of the distributed database environment can alter the impact of
a node outage on the other nodes. Table 13-4 on page 13-16 describes a modified
configuration in which only node \B contains application programs that query CAT_1
and CAT_2 objects as well as containing the CAT_1 and CAT_2 metadata. In this
\B Yes Yes Yes From nodes \A and \C, you
cannot perform DDL or utility
operations on CAT_1 or
CAT_2. You cannot perform
dynamically-compiled or
automatically-recompiled DML
operations on any CAT_1 or
CAT_2 objects. You cannot
perform statically-compiled
DML operations that require
data stored on node \B or late
name resolution of ANSI
names.
\C Yes No Yes From nodes \A and \B, you
cannot perform DDL or utility
operations on objects
partitioned across node \C.
You cannot perform statically-
compiled DML operations that
require data stored on node
\C.
Table 13-3. Consequences of Network Node Loss, Original Configuration
Node
CAT_1 and
CAT_2
User Data
Present?
CAT_1 and
CAT_2
Metadata
Present?
CAT_1 and
CAT_2
Applications
Present?
Consequences of Losing
This Node on the Other
Nodes