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ora-12203 TNS unable to connect to destination

amany_ahmed asked
Last Modified: 2013-12-11
i have installed 9i database and it is working well but the problem is in the form developer
it dose not connect to the database and gives me this error "TNS unable to connect to destination"
my processor is 'pentium 4' and my database is in the same computer and i am not using a network
please i need this help as soon as possible....thank you
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barthdevSolution Architect

Hi amany_ahmed,

Oracle uses a tnsnames.ora file which was probably written when you used the Net8 Configuration Assistant; by default it is stored in ORACLE_HOME\network\admin. That means that each ORACLE_HOME has it's own tnsnames.ora that it looks for.

You could copy the file from the ORACLE_HOME that's working to one that's not, but there are easier ways. I'm going to recommend that you set the TNS_ADMIN parameter in the registry.

Consider the following sample which has 9i database in HOME1 and form developer in HOME2.

Open 'regedit' and browse to the HOME1:

ORACLE_HOME = c:\oracle\ora91
[NEW KEY] TNS_ADMIN = c:\oracle\ora91\network\admin

ORACLE_HOME = c:\oracle\formsdev
[NEW KEY] TNS_ADMIN = c:\oracle\ora91\network\admin

This is your most likely difficulty. I'll be happy to give other suggestions or more detail if you ask.

Does that make sense?


Hi barthdev
 thank you for your help, but i have done what  you have told me but the error is still there .
it will be nice of you if you send me  any other suggestions.
barthdevSolution Architect


Start > Run > cmd
> cd c:\oracle\ora91\bin
(to your actual database home)
> tnsping <sid>
(your actual database sid)

What happens?

And what is your actual database home?

And how did you set your TNS_ADMIN?


you can use tnsping program to test definition and connection.

on ms-doc command prompt, write;

tnsping databasename

Top Expert 2008

Oracle Server <---> Developer 6i:
Oracle Developer6i and the Oracle8i database require separate Oracle home directories.
Even if you configure SQL*net (Net8) in the Oracle home that your database Oracle server uses, so that you can connect via SQL*Plus, that does not allow Developer2000 to connectsuccessfuly to the Oracle server.  You also need to configure SQL*Net (in tnsnames.ora file) in the
Oracle home for Developer2000.  You can do that either using the GUI tools, or to copy two files:
sqlnet.ora and tnsnames.ora from your 8i Oracle home to your Developer2000 Oracle home.  In your 8i
Oracle home these files are in: \Network\admin, but in your Developer2000 home they are in: \Net80\Admin. A safety measure is to save a copy of them first, before you make changes or copy other ones in. This is so because you have to keep a way for restoring the files if you make a mistake.
This is a generic advise I collected for a year answering to this kind of questions.
About connection between Personal Oracle and Forms 6 look at

You can use the "Oracle Net 8 assistant", "Oracle Net 8 Easy config" to see if you have the appropriate entry to the server in the local tnsnames.ora file (find it!). I mean that one in the Client or Forms&Reports home, not that one in the Oracle_Home.
Under local I mean the file tnsnames.ora  in your application, not at the Oracle Server - this is a common mistake.

You have to have there an entry like:

REKS816.RILA.us =
      (ADDRESS = (PROTOCOL = TCP)(HOST = bigbluenew.rila.us)(PORT = 1521))
      (SERVICE_NAME = REKS816)

Be aware that in old versions of Oracle instead of SERVICE_NAME you have to use SID. So (SERVICE_NAME = REKS816)will be (SID = REKS816)
It is a bad practice, but you can add such entry using simple text editor. But before that make a copy of tnsnames.ora in order to restore it if you do not succeed.


sorry for being late ,

i have tried the first soluation (tnsping) but my database use character set of(arabic) so it show me symbolic words which i cann't
understand .

the other soulation (changing in files) i tried it befor but it didn't work.

and by the way i checked up the file of the error detailes and it show me that  "there was
an error in protocol compatable"

and there is something else,
when i install the same versionof dev. on another pc which has  the same version of windows(2000) ,the developer connected to the database correctly, and the  other pc has no different hardware except the network card.

is this can make that difference ,cause really i want to know from where it comes that error.

thank you
Top Expert 2008
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