Specifications

Chapter 3. z/OS notes 25
will be picked up automatically at IPL time. The 60 second value shown here is arbitrary, but
should be safe. We suggest this not be done unless you experience spinloop problems.
3.4 Larger panel
The x3270 terminal emulator can be started with an optional parameter, as follows:
$ x3270 -port 3270 -oversize 133x60 localhost &
This produces a 3270 window with 133 columns and 60 lines. (Other sizes may be specified;
this is simply an example.) Basic TSO does not use the “extra” window space. ISPF can use it
if max is specified for the window format in the ISPF option 0 panel. (ISPF does not use the
extra width unless a data set being displayed or edited has records that can use the extra
width.)
3.5 z/OS disk space
Some z/OS functions assume certain disk allocations. For example, logger files may be
placed on the xxSYS1 volume. z/OS also places SVC dumps on this volume; a number of
these dumps can exhaust the free space on the volume. You can look for data sets with
names such as SYS1.ADCD.DMPnnnnn and delete them (assuming you are not working on
a problem that involves these dumps).
The exact data set name pattern for SVC dumps is sent in the appropriate COMMNDxx
member in PARMLIB.
For anything beyond trivial z/OS usage, we suggest that at least one more 3390 volume
should be defined and mounted as a STORAGE volume. An MVS command may then direct
SVC dumps to this new volume; the command would be similar to DUMPDS ADD,VOL=(volser).
3.6 Java and WebSphere Application Server startup
The IBM Java Virtual Machine (JVM) for zSeries® is designed and optimized for best
throughput performance on large mainframes. zPDT is sufficiently different in capabilities and
characteristics from traditional System z hardware so that certain Java applications may not
perform at their best without some tweaking of the JVM. This has been found especially true
for startup and installation types of workloads. Startup time improvements of 30-40% have
been seen on certain applications.
2
Be aware that, with the z/OS AD-CD system, some IPL options include Java in their
configuration and others do not.
3
If you cannot find java on your system, you may not have
used an IPL option that loads it.
This chapter provides some tips for improving the performance of Java-based applications.
They may or may not be useful in your particular Java use-case. A specific example is given
for tweaking the startup performance of IBM WebSphere Application Server v6.1.
2
Mitch Johnson (IBM USA) has investigated ways to improve IBM WebSphere® Application Server startup times on
smaller System z machines, including the 1090. This section is based on his work.
3
This is in the BPXPRMxx member of PARMLIB.