Introduction to NonStop SQL/MP

Distributed Database Architecture

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accesses is changed. For example, if a table is moved from one disk volume to another

or if a new index is created, application programs will still run. However, some SQL

queries might benefit by using the new index. You can choose when to schedule a

recompilation of the SQL queries to take advantage of the new database environment.

In a distributed database, NonStop SQL/MP can continue to process a query that

accesses several table partitions even if a partition is unavailable. That is, the database

remains available to the user even when a portion of the database is unavailable. The

user can optionally skip unavailable data. If some of the requested data resides on the

unavailable partition, the user still gets partial results.

NonStop SQL/MP also allows you to manage and reconfigure physical components of

the database online; that is, users can continue full read and write access to the

database while these management operations take place. For example, users can

continue to access the database while the DBA performs backup and restore

operations, loads data, and reorganizes files to maintain efficient access. Also, these

operations can be executed at a lower priority than user queries so that they have a

minimal impact on the performance of user applications.

You can perform the following tasks while the database is available for read and write

access:

Backing up the database

Restoring a part of the database from backup

Loading a portion of the database

Adding a partition to increase database size

The database is also available to user applications while you perform the following

tasks:

Moving a portion of a table’s data to another disk (possibly a larger or faster disk)

to balance I/O performance. This task is accomplished by splitting partitions or

moving partition boundaries.

Creating an index on a table or reorganizing an existing table or index for optimal

performance

At the end of these operations, however, the database is unavailable very briefly while

database file labels are updated to reflect the changed structure. You can schedule the

downtime so that it does not affect the execution of user queries.

Distributed Database

Architecture

A NonStop SQL/MP database can be fully distributed. You can partition tables and

indexes across systems in a network. (A system is called a node when it is part of a

network.) Moreover, NonStop SQL/MP provides location independence. You can

store data where it is used most frequently, and your applications can retrieve and

change the data regardless of where it is located. Accessing distributed data is as

simple as accessing local data: the applications provide the names of the tables that

contain the data. NonStop SQL/MP determines the location of the data as well as the

best way to retrieve it.