MX Database and Application Migration Guide

Converting SQL/MP Applications to SQL/MX

Applications

HP NonStop SQL/MP to NonStop SQL/MX Database and Application Migration Guide—666211-001

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Parallel Operations for Scalable High Performance

NonStop SQL/MX can perform some queries in parallel across multiple disk volumes

without the use of Executor Server Processes (ESPs). NonStop SQL/MP always

requires ESPs for parallel queries.

NonStop SQL/MX can execute large queries that scan large portions of the database in

parallel. NonStop SQL/MX supports three types of parallelism: pipelined parallelism,

independent parallelism, and partitioned parallelism. Pipelined and independent

parallelism are inherent features of NonStop SQL/MX, and you cannot force plans to

use them.

Partitioned parallelism is the ability to divide the data to be processed into partitions

and work on each partition in parallel. In a partitioned parallel plan, multiple operators

all work on the same plans, and results are merged by using multiple pipelines.

Although NonStop SQL/MP uses some partitioned parallelism to process in parallel,

NonStop SQL/MX takes advantage of both ESP parallelism and Data Access Manager

parallelism.

For more information about parallelism, see the

SQL/MX Query Guide.

Reasons for Keeping SQL/MP Applications

In some cases, it might be preferable to keep SQL/MP applications instead of

converting them to SQL/MX applications.

Large Number of Indexes

If you use many indexes in your SQL/MP database, reconsider converting the SQL/MP

applications to NonStop SQL/MX. The SQL compile time can be longer for SQL/MX

applications if there is a large number of indexes in your database. In NonStop

SQL/MX, an excessive number of indexes increases the search space for the optimal

plan.

Replicated Indexes on Multiple Nodes

Your SQL/MP database might use replicated indexes on multiple nodes so that a query

on a node can use the local index for access instead of a remote index. Be aware that

NonStop SQL/MX currently does not recognize this arrangement and might use a

remote index instead of a local index.

Single-Row Queries

Currently, single-row access has a smaller path length in NonStop SQL/MP than in

NonStop SQL/MX. If your SQL/MP application performs many single-row queries,

consider deferring the conversion of your application to NonStop SQL/MX. As NonStop

SQL/MX matures as a product, the set of queries that perform better in NonStop

SQL/MX are expected to grow.