| SQLITE_SHM_NLOCK(3) | Library Functions Manual | SQLITE_SHM_NLOCK(3) | 
SQLITE_SHM_NLOCK —
Maximum xShmLock index
The xShmLock method on sqlite3_io_methods may use values between 0 and this
  upper bound as its "offset" argument. The SQLite core will never
  attempt to acquire or release a lock outside of this range