Suddenly getting ORA-12514 error Oracle 11gr2

Question

I installed Oracle 11g r2 fine, had 2 databases (se3 and mydb, both have db_domain .orcl i.e. mydb.orcl and se3.orcl) running on it fine till yesterday. but suddenly im getting ORA-12514 error (TNS:listener doesn't know of service requested in connect descriptor)..
My tnsnames.ora file:
# tnsnames.ora Network Configuration File: G:\oracledb\product\11.2.0\dbhome_1\network\admin\tnsnames.ora
# Generated by Oracle configuration tools.
LISTENER_MYDB =
  (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
ORACLR_CONNECTION_DATA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    (CONNECT_DATA =
      (SID = CLRExtProc)
      (PRESENTATION = RO)
MYDB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = mydb.orcl)
SE3 =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = se3.orcl)
LISTENER_SE3 =
  (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
and my listener.ora file is as follows:
# listener.ora Network Configuration File: G:\oracledb\product\11.2.0\dbhome_1\network\admin\listener.ora
# Generated by Oracle configuration tools.
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = CLRExtProc)
      (ORACLE_HOME = G:\oracledb\product\11.2.0\dbhome_1)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ONLY:G:\oracledb\product\11.2.0\dbhome_1\bin\oraclr11.dll")
LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
ADR_BASE_LISTENER = G:\oracledb
* i have both of databases up and running(confirmed through administration assistant), the listener is up.. im able to execute "tnsping mydb/se3".. i'm not able to connect to either one of them through sqlplus/sql developer.. The result of "lsnrctl service" is as follows:
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
  TNS-00511: No listener
   32-bit Windows Error: 2: No such file or directory
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))
Services Summary...
Service "CLRExtProc" has 1 instance(s).
  Instance "CLRExtProc", status UNKNOWN, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0
         LOCAL SERVER
The command completed successfully
PLEASE HELP ME FRIENDS!! I HAVE A PROJECT DUE IN EARLY OCTOBER

Answer 1

Hi,
Instead of this:
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = CLRExtProc)
      (ORACLE_HOME = G:\oracledb\product\11.2.0\dbhome_1)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ONLY:G:\oracledb\product\11.2.0\dbhome_1\bin\oraclr11.dll")
LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
have the following in your listener file
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = CLRExtProc)
      (ORACLE_HOME = G:\oracledb\product\11.2.0\dbhome_1)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ONLY:G:\oracledb\product\11.2.0\dbhome_1\bin\oraclr11.dll")
   (SID_DESC =
      (SID_NAME = mydb)
      (ORACLE_HOME = G:\oracledb\product\11.2.0\dbhome_1)
    (SID_DESC =
      (SID_NAME = se3)
      (ORACLE_HOME = G:\oracledb\product\11.2.0\dbhome_1)   
LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
Also, dont have 'localhost' in your listener.ora file, provide the actual IP or hostanme. NEVER YOU should have
localhost.
Restart listener and try.
Thanks &
Best Regard,