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How to Improve Performance 5-23
Tuning Psort
Tuning Psort
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. Formaximum 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:
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