IBM 000-8697 Manual Do Utilizador

How to Improve Performance

If

PSORT_NPROCS

 is set to 0, Psort uses three as the default number of

processes for the sort.

When

PSORT_NPROCS

 is set to some number greater than zero, the value is

the maximum number of processes available. OnLine calculates the number
of sort processes to use given that constraint.

You maximize the effectiveness of Psort if you set

PSORT_NPROCS

 to the

number of available processors on the system. The maximum value for

PSORT_NPROCS

 is 10.

Each sort process must sort a minimum of 50 pages of data. That is, if you
specify five sort processes but only 125 pages of data require sorting, the
number of processes working on the sort is limited to two.

Set the

PSORT_NPROCS

 environment variable as follows:

A second environment variable,

PSORT_DBTEMP

, lists the directories that

OnLine uses for its intermediate writes. OnLine writes into the directories
listed in

PSORT_DBTEMP

in round-robin fashion. For maximum performance,

specify directories that reside in file systems on different disks. Ideally, the
disks should not contain any other frequently accessed files.

If

PSORT_DBTEMP

 is not set, OnLine uses the single directory named by the

environment variable

DBTEMP

. If

DBTEMP

 is not set, OnLine uses the

directory /tmp.

When you specify more than one directory, separate the directory names
with a colon. Set the

PSORT_DBTEMP

 environment variable as follows:

setenv PSORT_NPROCS num_of_processes

PSORT_NPROCS=num_of_processes

export PSORT_NPROCS

setenv PSORT_DBTEMP directory:directory

PSORT_DBTEMP=directory:directory

export PSORT_DBTEMP