ORA-12545: Connect failed because target host or object does not exist

OK, Almost everbody who has worked in Oracle would have seen this error message. This is one of most frustrating and most common error

What does "ORA-12545: Connect failed because target host or object does not exist"  mean ?


Say from SQLPlus, you are issuing the following command

SQL> Conn scott/tiger@orcldb;

SO, SQLPlus, looks for the entry "orcldb" in your client tnsnames.ora file.

In tnsnames.ora, you will find an entry something similar to this

orcldb=
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = <db_machine_name or ip address>)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = db_name)
    )
  )

so "ORA-12545: Connect failed because target host or object does not exist" means, either your db_machine_name/ip address is incorrect or your machine cannot connect to db_machinge_name/ip_address
for various reasons like network issues etc