SQL> @waiters

EVENT                           T0   T1   T2   T3   T4   T5   T6   T7   T8   T9
----------------------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
control file parallel write                                              1
direct path read                 1
file open                                  1
LGWR wait for redo copy                                                  1
db file scattered read                                         1    1
SQL*Net message from dblink      1    1
SQL*Net more data from client                        1                        1
control file sequential read                    1    1         1         1    1
buffer busy waits                               1    1    1    1    1    1    1
direct path write                     1    1    1    1    1    1    1    1    1
db file sequential read                         1    2    3    3    2    1    1
enqueue                                         1    2    2    2    2    2    2
log file sync                         2    1    1         6         3
SQL*Net message to client        2    4    3    4    2    2    2    2    2    2
latch free                     183  136   14   17   32   44   78  104  122  143