ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

Don't know why the oracle standby db can't be reached by primary database suddenly (which is working perfectly before). After googling the problem, i found the solution by adding the following into listener.ora:

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = D:\oracle\product\10.2.0\db_1)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = visdev2)
(ORACLE_HOME = D:\oracle\product\10.2.0\db_1)
)
)