The "JVM Trace Options" display is produced by pressing PF6 on the main CETR display. You can use these screens to display and update trace settings for JVMs. (Although the JVM trace options are part of the SJ component, they are controlled using the JVM trace options screens, rather than the component trace options screen.)
You can use these screens to specify the JVM trace options, using the "free-form" 240-character field, and to specify trace settings for JVMs using the Standard and Special flags. You can then use the Transaction and Terminal Trace screen to switch on these flags for particular transactions. JVM trace can produce a large amount of output, so you should normally activate JVM trace for special transactions, rather than turning it on globally for all transactions.
There are two JVM trace options screens, one for JVM Level 0 trace and JVM Level 1 trace, and one for JVM Level 2 trace and JVM User trace. The screens display the trace flags and the trace options strings associated with each flag. Press PF8 to move to the second JVM trace options screen, and PF7 to move from there back to the first screen. Set any of the trace options to ‘*’ to reset the option to its default settings, or press PF6 to reset all of the JVM trace options to their default settings. Press PF3 to return to the CETR main screen, and press Enter on any screen to pass the changes to CICS.
The display layout is as follows:
CETR JVM Trace Options CJB2 IYK2Z1V2 Type in your choices. PAGE 1 OF 2 Item Standard Special JVM Level 0 Trace ===> OFF ON, OFf ===> OFF ON, OFf Option String: LEVEL0 JVM Level 1 Trace ===> OFF ON, OFf ===> OFF ON, OFf Option String: LEVEL1 When finished, press ENTER. PF1=Help 3=Quit 6=Reset 8=Forward 9=Error List
CETR JVM Trace Options CJB2 IYK2Z1V2 Type in your choices. PAGE 2 OF 2 Item Standard Special JVM Level 2 Trace ===> OFF ON, OFf ===> OFF ON, OFf Option String: LEVEL2 JVM User Trace ===> OFF ON, OFf ===> OFF ON, OFf Option String: NONE When finished, press ENTER. PF1=Help 3=Quit 6=Reset 7=Back 9=Error List
The default JVM trace options that are provided in CICS use the JVM trace point level specifications. The default settings for JVM Level 0 trace, JVM Level 1 trace, and JVM Level 2 trace specify LEVEL0, LEVEL1, and LEVEL2 respectively, so they map to the Level 0, Level 1 and Level 2 trace point levels for JVMs. A Level 0 trace point is very important, and this classification is reserved for extraordinary events and errors. Note that unlike CICS exception trace, which cannot be switched off, the JVM Level 0 trace is normally switched off unless JVM tracing is required. The Level 1 trace points and Level 2 trace points provide deeper levels of tracing. The JVM trace point levels go up to Level 9, which provide in-depth component detail.
It is suggested that you keep the CICS-supplied level specifications, but if you find that another JVM trace point level is more useful for your purposes than one of the default levels, you could change the level specification to map to your preferred JVM trace point level (for example, you could specify LEVEL5 instead of LEVEL2 for the JVMLEVEL2TRACE option). Note that enabling a JVM trace point level enables that level and all levels above it, so for example, if you activate JVM Level 1 trace for a particular transaction, you receive Level 0 trace points for that transaction as well. This means that you only need to activate the deepest level of tracing that you require, and the other levels are activated as well.
You can add further parameters to the basic level specifications for JVM Level 0 trace, JVM Level 1 trace, and JVM Level 2 trace, if you want to include or exclude particular components or trace point types at the selected trace levels. If you want to create more complex specifications for JVM tracing which use multiple trace point levels, or if you do not want to use trace point levels at all in your specification, use the JVMUSERTRACE option to create a trace option string that includes the parameters of your choice. "Defining tracing for JVMs" in the CICS® Problem Determination Guide has information about the JVM trace options that you can set using the JVM Level 0 trace, JVM Level 1 trace, JVM Level 2 trace, and JVM User trace levels. There is further information about JVM trace and about problem determination for JVMs in the IBM® Developer Kit and Runtime Environment, Java 2 Technology Edition, Version 1.4.2 Diagnostics Guide, SC34-6358, which is available to download from www.ibm.com/developerworks/java/jdk/diagnosis/.
Trace levels 29-32 for the SJ component correspond to JVM Level 0, Level 1, Level 2, and User trace respectively. When you activate JVM trace, each JVM trace point that is generated appears as an instance of CICS trace point SJ 4D01. If the JVM trace facility fails, CICS issues the trace point SJ 4D00.
As well as using CETR, you can also control JVM trace by using:
When CICS starts to use or re-use a JVM, it ensures that any trace options that you have set and activated using CETR are applied. Activating or deactivating a trace option using CETR overrides any setting for that trace option in the ibm.dg.trc.external system property. For example, a trace option that is activated in the system property, but deactivated using CETR, will be deactivated when CICS starts to use or re-use the JVM. If you use CETR to activate any trace options that are not referred to in the ibm.dg.trc.external system property, the trace options that you have specified in CETR are added to any trace options that you have set using the ibm.dg.trc.external system property. The trace output will then reflect all the trace options that you requested in both CETR and the system property.
tells you about these alternative ways to control tracing for your JVMs.