GV$LOCK_ACTIVITY definition in Oracle Database 11.2
GV$LOCK_ACTIVITY

select
  0,                                       -- INST_ID NUMBER
  'NULL',                                  -- FROM_VAL CHAR(4)
  'S',                                     -- TO_VAL CHAR(1)
  'Lock buffers for read',                 -- ACTION_VAL CHAR(21)
  0                                        -- COUNTER NUMBER
from
  dual

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