How to Improve Performance 5-23

Tuning Psort

Tuning Psort
IfPSORT_NPROCS is set to 0, Psort uses three as the default number of
processes for the sort.
WhenPSORT_NPROCS is set to some number greater than zero, the value is
themaximum number of processes available. OnLinecalculates the number
of sort processes to use given that constraint.
You maximize the effectiveness of Psort if you setPSORT_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 thePSORT_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
listedin 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 variableDBTEMP. 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:
C shell: setenv PSORT_NPROCS num_of_processes
Bourne shell: PSORT_NPROCS=num_of_processes
export PSORT_NPROCS
C shell: setenv PSORT_DBTEMP directory:directory
Bourne shell: PSORT_DBTEMP=directory:directory
export PSORT_DBTEMP