Log file sync is a client wait event. It is the wait event your clients wait on when they say "commit". It is the wait for LGWR to actually write their redo to disk and return back to them. You can "tune" this by making lgwr faster (no raid 5 for example) and committing less frequently and generating less redo (BULK operations generate less redo than row by row do) The other one is a background wait. LGWR is waiting for forgrounds to finish a current copy affecting the data LGWR is about to process. HOWEVER, that said, tuning either of these will have no noticable affect on your systems performance whatsoever! It certainly looks like "enqueue" is your wait and that is all about application design - those are heavyweight locks induced by the application logic itself. You would be best served by looking at the *application* not at the "system" at this point.
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