select mysum( 2 , 2 ) from dual
                       *
ERROR at line  1 :
ORA- 06520 : PL/SQL: Error loading external library
ORA- 06522 : Unable to load DLL

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
      )
      (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = TCP)(HOST = vinga-gleb)(PORT =  1521 ))
      )
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = C:\oracle\ora92)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ANY")
    )
    (SID_DESC =
      (GLOBAL_DBNAME = primary)
      (ORACLE_HOME = C:\oracle\ora92)
      (SID_NAME = primary)
    )
    (SID_DESC =
      (GLOBAL_DBNAME = rep)
      (ORACLE_HOME = C:\oracle\ora92)
      (SID_NAME = rep)
    )
  )

EXTPROC_CONNECTION_DATA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
    )
    (CONNECT_DATA =
      (SID = PLSExtProc)
      (PRESENTATION = RO)
    )
  )

create or replace library testlib
as 'D:\temp\uiu.dll';

CREATE OR REPLACE function MySum (a       IN      binary_integer,
                                  b       IN      binary_integer ) return binary_integer IS
LANGUAGE C
NAME "ExtPow"
LIBRARY testlib 
--WITH CONTEXT
PARAMETERS (
      --context,
      a      int,
      b      int);
      

#include <math.h>

extern "C" __declspec(dllexport) int ExtPow(int  a, int b);

__declspec(dllexport) int ExtPow(int  a, int b)
{
 return pow((double)a,(double)b);
}