Chapter 5. Tuning iSeries for a WebSphere or Java environment 169
If you use the automatic tuner, but want to manually set up the size and activity level settings
for a pool, then follow these steps:
1. Enter the Work with Shared Pools (WRKSHRPOOL) command.
2. Press F11 for the tuning data.
3. Set the minimum pool size equal to maximum pool size.
This tells the automatic tuner not to adjust this pool.
5.3.3 Verifying the settings of system values
System values are to the jobs running on an iSeries server what properties are to Java. They
define the basic characteristics of the operating system and all the jobs being supported by
the operating system.
There are several system values that you should consider changing by using either the
Change System Value (CHGSYSVAL) or Work with System Value (WRKSYSVAL)
commands. The following sections describe each of these system values and the
recommended settings. The recommended numbers have been found to work in hundreds of
Allocation system values
Every job on the iSeries server has a Work Control Block Table (WCBT) entry that the
operating system uses to keep track of the jobs in the system. A WCBT entry can be seen as
a pre-fabricated frame for a job that is filled with the jobs’ run attributes by the time the job
becomes active within a subsystem. A job holds the WCBT entry as long as the job is active
and as long as even one spooled output file exists for the job on the system.
The allocation system values are:
QACTJOB: Initial number of active jobs
QADLACTJ: Additional number of active jobs
QADLSPLA: Spooling control block additional storage
QADLTOTJ: Additional number of total jobs
QJOBMSGQFL: Job message queue full action
QJOBMSGQMX: Maximum size of job message queue
QJOBMSGQSZ: Job message queue initial size
QJOBMSGQTL: Job message queue maximum initial size
QJOBSPLA: Spooling control block initial size
QMAXJOB: Maximum number of jobs
QMAXSPLF: Maximum spooled files
QRCLSPLSTG: Reclaim spool storage
QTOTJOB: Initial total number of jobs
First verify the settings of the allocation system values on your system. In some cases, this
may be the only action that you need to remove the performance problem. The following
sections discuss the most important system values and their settings.
QTOTJOB (Initial total number of jobs)
This specifies the initial number of WCBT entries created during the initial program load (IPL).
You have two options to determine the required setting of this system value:
Work with System Status (WRKSYSSTS) command
Display Job Tables (DSPJOBTBL) command