How do I change the prefix output on every trace line?

Use the following command to change the prefix output on every trace line:

set TRACE_FORMAT_PREFIX=[%9!d!]%8!04X!.%3!04X!::%4!s! [%1!s!] 
tracefmt -f mytracefile 

For information about the TRACE_FORMAT_PREFIX parameters, see the Trace Message Prefix topic.