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Troubleshooting Oracle-1 (Not able to connect to the DB) Print E-mail

Today we have the certain troubleshooting that can be done with Oracle.

1.      Not able to connect to the DB.

Error Messages encountered:
TNS-03505: Failed to resolve name
ORA-12154: TNS:could not resolve the connect identifier specified

The possible solutions can be
a.      If the error message is like Check if TNSPING is working from the command shell. For this you need to run “tnsping DB_identifier”. The DB_identifier is a string for which the Oracle client will search in the “tnsnames.ora” file. For example

 

 

DB_string =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.XX.XX.XXX)(PORT = 1521))
    (CONNECT_DATA =
      (SERVICE_NAME = DB.WORLD)   )  )

 

Here the DB_identifier is “DB_string”. This can be any string. The service name here is DB.WORLD, this is DB specific here and has to be same everywhere.
If no response is observed from the above tnsping command then you need to check if the DB_identifier that you are using is present in the tnsnames.ora file.

b.      There are issues with the formatting of the tnsnames.ora entry. So In case of problems we can copy some other block and paste the same in tnsnames.ora file and change the DB_identifier,Service Name and the IP address as per our requirements.

c.      Check the network connectivity of the DB. If you can ping the IP address of the DB? If there is no response from the DB then it does not always mean that the DB is down. Your ping might be blocked on the server or on the network.

d.      Check if the correct tnsnames.ora file is used.If you have multiple Oracle installations like

Oracle app server
Oracle Client
Oracle DB server

Then the thumb rule is to use the tnsnames.ora file of the Oracle software which was installed last.
Also you could add an entry to the correct tnsnames.ora by using NETCA (Oracle Network configuration Assistant).This will pick up the current tnsnames.ora file from the current ORACLE_HOME environment.

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