Introduction to NonStop SQL/MP

Scalability

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NonStop SQL/MP uses the the NonStop Transaction Manager/MP (TM/MP)

subsystem to maintain data consistency amid concurrent transactions. The

NonStop TM/MP subsystem ensures that data modifications are either completely

applied to the database or not performed at all. NonStop TM/MP automatically backs

out any incomplete transactions and manages recovery in case of system or media

failures. A NonStop SQL/MP database thus remains in a consistent state even if, for

example, a communication line failure interrupts a transaction.

NonStop SQL/MP is also integrated with system utilities that help configure and

manage software in a Tandem system, with the Measure performance measurement

tool, which collects performance statistics on processes and tables, and with system

monitoring and event management tools.

Table Partitioning and

Parallel Execution

NonStop SQL/MP allows you to partition the data in a table across many disk

volumes. You can configure your hardware system so that the disk volumes (and,

thus, the table partitions) are managed by different processors within a system or

different processors across a distributed network. Partitioning the database allows

NonStop SQL/MP to take full advantage of the parallel processing provided by the

Tandem multiprocessor architecture.

Multiple NonStop SQL/MP executor processes can execute in parallel in separate

processors. The SQL executors can process multiple small queries in parallel. For a

large query, an SQL master executor process can create executor server processes that

divide up the query into smaller tasks and process the tasks in parallel.

The SQL executors can use separate data access managers to retrieve data from the

partitions associated with their processor. This strategy balances the I/O workload

among the multiple processors, greatly improving both throughput (the total data the

system can process at one time) and response time (the elapsed time it takes to

complete one user transaction). In addition, you can partition indexes across disk

volumes to provide faster access to the data.

NonStop SQL/MP also performs the following tasks in parallel:

Parallel join operations by the SQL executor during query processing

Parallel index maintenance, which reduces the effect of multiple indexes on

performance

Parallel sorting of large amounts of data by the FastSort utility

These features make it possible for a Tandem system to perform massively parallel

processing against a very large database. Moreover, these features allow you to scale a

database to a larger and larger size as your application requirements grow, without

affecting performance.