Chapter 5. Performance tuning 115
5.2.3 Subsystems and memory pools
By default, WebSphere jobs run in the QEJBSBS subsystem in the base memory pool. In
addition, WebSphere applications, such as call.connect and vendor.connect, substantially
use the native JDBC server jobs that run in QSYSWRK. This is also in the base memory pool,
by default.
If your system runs no other significant applications, then this simple setup may be sufficient.
The resource usage of WebSphere applications is quite different from traditional interactive
and batch jobs. Therefore, if you also run these types of jobs, it may be preferable to use a
separate memory pool. A separate memory pool allows you control the resources allocated to
WebSphere applications. You can enhance WebSphere performance, possibly at the
expense of others jobs, by increasing its memory pool. Or you can reduce the impact on other
applications by reducing it.
You can set up separate pools for the QEJBSBS subsystem and the QSQSRVR jobs, but in
most cases, this is unnecessarily complicated to manage. If the two are combined, then you
must have a shared pool.
Ideally, you should know the configuration of your system and know which shared pools are
available. You can see if a shared pool is currently in use by using the WRKSYSSTS
command.
On the Work with System Status display (Figure 5-7), press F11 until you see the Pool
column. In this column, you will see such names as *MACHINE, *BASE, *INTERACT, and
maybe *SHRPOOL1, *SHRPOOL2, etc. You can also use the Work with Shared Pool
(WRKSHRPOOL) command. If the defined size and maximum active values are both zero,
then the pool may never have been used.
This example assumes shared pool 1, but any other can be substituted. In Figure 5-7, a
shared pool is already setup for WebSphere. Shared pool 2 was used.
Figure 5-7 WRKSYSSTS command showing the memory pool names
You need to specify the memory size and activity level. If possible, specify at least 500 MB
and better still, specify 1 GB. If your client will be busy, then set the activity level to
approximately the number of users. You can adjust both figures once the system is configured
and used.
To set up a shared pool for WebSphere and the SQL server jobs, follow these steps:
1. End any WebSphere applications, WebSphere itself, and any other Java applications that
are using the native JDBC driver.
