Error while connecting to oracle DB

I have an error while trying to connect to oracle db.

The error is:

ORA-12154: TNS:could not resolve the connect identifier specified

When i launch the application and login, sometimes 开发者_开发知识库this error occur and sometimes not. in other words when logging into the system, the error pops only for certain users!

what might be the issue?

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There might be a problem with the TNSNAMES.ORA file in the Oracle Client installation for those affected users. Check the TNS definitions.

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This is 98% of the time an issue on the user's client (typically PC) with missing/wrong tnsnames.ora and/or sqlnet.ora files. Since it works for some users, make sure the files sqlnet.ora and tnsnames.ora exist for the problem users, and that they are the same version. You can also check the value of registry variable TNS_ADMIN, and look for the presence of multiple oracle homes. Sometimes developers inadvertently modify this situation by installing extra goodies, and then they don't pick up new changes.