prof_enable is used to enable or disable 
    profiling of execution times, SQL statements and web requests.  
    Passing flag value 1, enables profiling, causing times of statement 
    executions, which begin and end while profiling is on, to be 
    accumulated.When called with a flag of 0, the accumulation is stopped and 
    results gathered so far are written into file named virtprof.out in 
    the server@s working directory.  For a description of the file, see 
    section about SQL Execution Profiling 
    in Performance tuning part of 
    Virtuoso documentation.