Using the WITH APPEND Option
The output file that you specify in the SET DEBUG FILE statement can be a new file or existing file. If you specify an existing file, its current contents are deleted when you issue the SET DEBUG FILE TO statement. The first execution of a TRACE statement sends trace output to the beginning of the file.
If you include the WITH APPEND option, the current contents of the file are preserved when you issue the SET DEBUG FILE statement. The first execution of a TRACE statement adds the new trace output to the end of the file.
If you specify a new file in the SET DEBUG FILE TO statement, it makes no difference whether you include the WITH APPEND option. The first execution of a TRACE statement sends trace output to the beginning of the new file whether you include or omit the WITH APPEND option.