Maximum Performance with WebSphere Application Server V5.1 on iSeries

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

real-life cases.

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