Int 2F Fn 120B  U - Dos 3.0+ Internal - Signal Sharing Violation To User   [D]

   AX = 120Bh
   ES:DI -> system file table entry for previous open of file
   STACK: WORD extended error code (should be 20h--sharing violation)

Return: CF clear if operation should be retried
   CF set if operation should not be retried
       AX = error code (20h) (see #1366 at INT 21/AH=59h/BX=0000h)
   STACK unchanged

Notes: can only be called during a DOS function call
   should only be called if an attempt was made to open an already-open
     file contrary to the sharing rules
   invokes INT 24 if SFT file opened via FCB or in compatibility mode with
     inheritance allowed