Activating and Deactivating Developer Traces 
Procedure
You can turn developer traces on and off and set the trace level dynamically from within the SAP System or using system profile parameters or command-line arguments.
Activating and Deactivating Developer Traces from within SAP System:
Choose
Administration 
System Administration Monitor System Monitoring Process Overview 
or enter transaction SM50.Choose the work process(es) for which you want to increase the trace level.
Choose
Process Trace Active Components .The system presents a dialog screen that shows the current status of the developer trace.
Turn developer tracing on and off for different server components by selecting the appropriate checkboxes.
Set the degree of detail by entering a number in the Level field. Possible trace levels are as follows:
0: No trace
1: Write error messages in the trace file.
2: Full trace. The trace entries that are actually written can vary with the program that is being traced.
3: Additionally, trace data blocks.
Activating and Deactivating Developer Traces from the System Profile
You can also set trace options instance-wide with parameter rdisp/TRACE=<n>. The trace values are the same as those in the list above.
Setting the trace parameter in the instance profile of a particular server activates developer traces only in that server.
Setting the parameter in the default profile would activate traces in all servers (excepting those whose instance profiles specify a different parameter value).
Activating and Deactivating Developer Traces from the Command Line
You can also manage trace behavior using commands in the command line. This is possible in all SAP programs. Typically, you must add these options to the start commands for SAP processes in the start-up profile of an instance of your SAP system.
You can use the following options:
TRACE=0: No trace
TRACE=1: Write error messages in the trace file.
TRACE=2: Full trace. The trace entries that are actually written can vary with the ABAP program that is being traced.
TRACE=3: Additionally, trace data blocks.
For information on editing start profiles see the documentation for the Computing Center Management System Guide (CCMS).
Further Procedure
You can then view the traces in the system or at operating system level, or download them to your local computer. The sections below contain more details: