Introduction to NonStop SQL/MP

Scalability

1–8 113425 Tandem Computers Incorporated

Scalability A NonStop SQL/MP database is scalable—you can expand the size of the database

simply by adding processors and disk volumes to the system. You do not have to

change application code when you scale up the database. As the database and

application grow, you can maintain the high performance of the original, smaller

database. Moreover, you can speed up the performance of a database that is not

growing—again, simply by adding processors and disk volumes.

Tandem’s Parallel

Hardware Architecture

The scalability of a NonStop SQL/MP database is founded on the parallel hardware

architecture of Tandem systems. A Tandem system contains from 2 to 16 processors,

each with its own memory and disk storage, linked by a pair of high-speed

interprocessor buses (IPBs). Because the processors do not share memory or disks, this

is sometimes called a shared-nothing architecture.

The processors communicate by sending messages over the IPB, following a model

similar to the client/server model. A client process executing in any processor submits

a request for a service. A server process executing in the same processor or another

processor responds to the request.

A typical transaction or request for database services comprises several client/server

interactions. Suppose an end user running a program on a PC requests data. An

application process on the Tandem host serves the request by calling

NonStop SQL/MP, which passes the request to the data access manager (DP2), which

retrieves the data from disk and passes it back. These processes can be distributed

across the system (or across a network) so that no single processor is excessively

burdened by a request.

When you add a processor to the system, the expansion in performance is linear—that

is, the performance you get from the added processor is exactly the same as that of the

first processor in the system. Linear expandability is possible because the processors

do not share resources (memory and disks). A shared resource can cause a

performance bottleneck when you expand the system, as the additional components

all contend for use of the shared resource.

The Tandem TorusNet networking technology allows you to expand beyond a single

system and connect up to 4,080 processors in a single network. A process executing

anywhere in the network has easy access to any other process or resource in the

network. Because of the message-based operating system, it makes no difference

whether the process serving a request is located in the local system or in a system

elsewhere on the TorusNet network.

Figure 1-3 shows how an application process in one system requests data from

NonStop SQL/MP, which uses the message system to process the request, retrieving

data from both a local and a remote system.