SQL/MP Installation and Management Guide

HP NonStop SQL/MP Installation and Management Guide—523353-004

12-1

Managing a Distributed Database

Databases can be distributed over disk volumes on a single system (node) or in a

network of nodes. Likewise, application programs can be distributed across processors

in a single node or in a network.

When managing a database distributed across volumes or nodes, use the same SQL

statements you would use with a nondistributed database. When accessing a

distributed SQL object, some SQL statements enable you to use distinct file names

that refer to individual partitions of the object. For other statements, however, a

partition name refers to the entire object rather than to the individual partition.

The distribution issues discussed in this section are divided into the general areas of

locally distributed databases (distributed over two or more disk volumes on the same

node) and network-distributed databases.

Managing a Locally Distributed Database

An SQL/MP database is locally distributed if any tables, views, or indexes are

partitioned over two or more volumes. The goals for managing a locally distributed

database are:

•

Using the total available processing power of the system while balancing the

workload

•

Enabling very large data files to physically spread across multiple disk volumes

while accessed as single files

Using DEFINEs for Logical Name Mapping

When you are working with distributed objects, you should always fully qualify each

reference, either in each statement or by using DEFINEs.

Use DEFINEs for a distributed database in the same way you would for a

nondistributed database. You might want to create DEFINE names for each partition of

the object because the partitions might be accessed separately. For a distributed

object, you can include the partition number in the DEFINE name to avoid any

confusion about the applicable partition in this format:

=partition-number_define-name

These DEFINE names are examples of distributed names:

=PART1_EMPLOYEE, CLASS MAP, FILE \LOCAL1.$VOL1.PERSNL.EMPLOYEE

=PART2_EMPLOYEE, CLASS MAP, FILE \LOCAL1.$VOL2.PERSNL.EMPLOYEE