TNS-12557: TNS:protocol adapter not loadable.Oracle may not configured properly

Hello Everyone!In my office I had oracle 9i  client installed on my PC.I used it to connect to our production database server(Dont know where it is!) which is 11g.Problem occurred when I installed Oracle 11g R2 (both client and server ) on my pc.

I was able to connect  to local  server(my machine) using  sqlplus. But failed to connect to our production server using sqlplus,but it was okay with other devices like Toad. My daily job was at a stake!

I received error massage like: TNS-12557: TNS:protocol adapter not loadable.Oracle may not configured properly. The main reason behind this is that Windows Command prompt doesn’t know which sqlplus to connect with,cause it got multiple location entry for  Oracle clients.To check out follow the steps.

1. Go to windows run prompt.( windows +R)

2.Type sysdm.cpl and hit enter.


3.From the System Properties window choose Advanced tab & click on the Environment Variables button. A new window will appear.

4. Double click on the Path variable of the System variables section. In the ‘edit system variable’ window check  ‘Variable value:’  text-box. You can see there are two links for  …..\Oracle\…\bin folder.(links are separated by ‘;’). In usual case,the first link is used as the default oracle client regardless of the second link. But this creates problem sometimes and shows error.

So I deleted one and kept the one I want to use as my oracle client.So when I typed ‘sqlplus /nolog’ on my cmd prompt ,it worked fine.

5. But this doesn’t mean I cant use my other Oracle Client(11g in my case). We have to type the whole address of bin folder link in the cmd prompt.

The picture depicts everything.9i is the default client. But I want to use my 11g client to browse my local 11g database.In cmd prompt I went to bin directory and started sqlplus.Here md.towhidul is my pc username. Then typed sys as sysdba as user name and kept password blank. Here using  ‘/’ instead of ‘sys’ wont work which works in case of  default cmd>sqlplus / as sysdba.

Hope this helps. Lemme know your feedback.Have fun!