(ZOS) Internal tracing tips for WebSphere for z/OS

WebSphere Application Server traces can be extremely helpful in detecting and diagnosing problems.

By properly setting trace options, we can capture the information needed to detect problems without significant performance overhead.

• Ensure that we are not collecting more diagnostic data than we need.

  We should check the WebSphere for z/OS tracing options to ensure that ras_trace_defaultTracingLevel=0 or 1, and that ras_trace_basic and ras_trace_detail are not set.

  How to view or set: Use the WebSphere administrative console:

  1. Click Environment > Manage WebSphere Variables.

  2. On the Configuration Tab check for any of these variables in the name field and observe the variable setting in the value field.

  3. To change or set a variable, specify the variable in the name field and specify the setting in the value field. We can also describe the setting in the description field on this tab.

• For the best performance with any level of tracing, including ras_trace_defaultTracingLevel=1, set ras_trace_outputLocation to BUFFER. This trace setting stores the trace data in memory, which is later asynchronously written to a CTRACE data set. Setting ras_trace_outputLocation to SYSPRINT or TRCFILE provides approximately the same level of performance, but significantly less than BUFFER.

• Use the ras_trace_BufferCount and ras_trace_BufferSize settings to control the amount of storage used for trace buffers. Generally, the larger the buffer allocation, the better the performance. However, specifying a buffer allocation that is too large can cause a decrease in performance due to system paging.

  The default settings of ras_trace_BufferCount=4 and ras_trace_BufferSize=1M should perform sufficiently for most applications.

• Make sure you disable JRAS tracing.

  To do this, look for the following lines in the trace.dat file pointed to by the JVM properties file:

  com.ibm.ejs.*=all=disable
  
  com.ibm.ws390.orb=all=disable
  
  
  

  Ensure that both lines are set to =disable or delete the two lines altogether.

  If ras_trace_outputLocation is set, you may be tracing and not know it.

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