SQL/MP Installation and Management Guide

Managing a Distributed Database
HP NonStop SQL/MP Installation and Management Guide—523353-004
12-2
Maintaining Local Autonomy
Maintaining Local Autonomy
Local autonomy implies that a DML request, initiated either interactively or with an
application program, can access local data, regardless of the availability of remote
dependent objects or other local dependent objects if the local data can satisfy the
request.
For example, if a table named PARTS is partitioned with a partition on $VOL1 and
another partition on $VOL2, a query of PARTS can access the partition on $VOL2
regardless of the availability of $VOL1. The $VOL2 partition can be opened upon
demand for its access if the CONTROL TABLE OPEN ACCESSED statement is in
effect.
Similarly, if a query tries to access the table named EMPLOYEE, residing on $VOL2,
through an index named IEMP2, residing on $VOL1, the query can be completed
regardless of the availability of $VOL1. If $VOL1 is not available, SQL/MP
automatically tries to find an alternate path. For more information about access paths,
see Maintaining Local Autonomy in a Network on page 12-5.
Managing a Network-Distributed Database
NonStop systems can be linked together by communication lines to create a network.
Each system on the network is called a node.
An SQL/MP database or application can be distributed over a network of nodes in
several ways:
•
Tables or indexes are partitioned over two or more nodes.
•
Tables, indexes, views, or programs reside on two or more nodes.
•
A local shorthand view or index references a remote base table.
•
Local programs access remote tables or views or use a remote access path.
•
Remote programs access local tables, views, or indexes.
The goals for managing a network-distributed database area follows:
•
Efficiently share data among users located remotely from one another.
•
Allow for local identity and control while sharing information.
•
Eliminate duplication of data.
•
Increase the local computing power by the aggregate total of the computing power
of the network.