SQL/MX 2.x Installation and Management Guide (H06.10+, J06.03+)

Managing an SQL/MX Distributed Database
HP NonStop SQL/MX Installation and Management Guide—544536-007
13-16
Maintaining Local Autonomy in a Network for
SQL/MX Release 2.x
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 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 revised
configuration, node \B becomes more of a single point of failure for the distributed
database.
Clearly, the configuration described in Table 13-4
has less local autonomy than the
configuration described in Table 13-3
. Because node \B represents a single point of
failure, this configuration is not advisable in a geographically distributed environment.
However, in a locally distributed environment where all three nodes are in the same
computer room and a reliable high-speed network interconnect is used, the risks of this
configuration are reduced.
Depending on the interrelationships between the involved catalogs, you might want to
implement the configuration described in Table 13-5. In this configuration, CAT_1 is
created on node \A and CAT_2 on node \B, so their respective object metadata remain
on these two nodes.
Table 13-4. Consequences of Network Node Loss, Reconfiguration 1
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
\A Yes No No The same consequences
occur as were identified in the
node \A row in Table 13-3
.
\B Yes Yes Yes The same consequences
occur as were identified in the
node \B row in Table 13-3
. In
addition, none of the
applications that contain
queries to CAT_1 or CAT_2
can be executed.
\C Yes No No The same consequences
occur as were identified in the
node \C row in Table 13-3
.