FastSort Manual

FastSort Manual—429834-003

7-1

Using SORT and SUBSORT DEFINEs

Before you start a sort or merge run, you can set or change operating system

parameters that affect FastSort. While the FastSort default settings are often sufficient

for small sort or merge runs, modifying the default settings can improve the

performance of a large run.

You modify default settings for a sort operation with CLASS SORT and SUBSORT

DEFINEs. You can set or change a DEFINE either interactively or programmatically.

Tasks you can perform with SORT and SUBSORT DEFINEs include:



Select a less busy processor for SORTPROG processes



Select a disk with more free space than the default for your initial scratch file



Manually specify certain parameters that are difficult to set from an application

program



Specify parameters for sorting from SQL/MP and other products that do not allow

you to specify FastSort parameters at run time

This section describes the following FastSort DEFINEs:

SORT DEFINE

is the FastSort DEFINE you use to control the SORTPROG process in a serial sort

run or the distributor-collector SORTPROG process in a parallel sort run.

SUBSORT DEFINE

is the FastSort DEFINE you use to control a subsort process in a parallel sort run.

You can specify 2 to 8 SUBSORT DEFINEs to set parameters for each subsort

process that is linked to a specific SORT DEFINE.

=_SORT_DEFAULTS DEFINE

is the FastSort default DEFINE. You use this DEFINE to specify FastSort

parameters for SQL/MP and applications that otherwise cannot set the parameters.

Section 8, Sorting From NonStop SQL/MP contains additional information about

configuring sorts from SQL/MP.

Determining the Precedence of DEFINEs

There are four possible ways to specify FastSort parameter values. If a conflict occurs

between two or more values, FastSort chooses a value as follows: