connection issue

The connect string u are using trying connect during export/toad is not find in ur tnsnames.ora. Hopefully you are using different (or probably not using any of) connect string while connecting from sqlplus/oem,so u r getting connected. Please do check ur tnsnames.ora file.

Do you use a connect string for SQL*Plus or OEM?  If so, what is it?  Do you run all of these programs on the same machine, or do you run some of them on the server and some on a client?  Do you have multiple Oracle_homes?  If so, SQL*Net may be configured differntly in one of them than in the other(s).

i installed oracle personal database on my machine . i do have client as well, when i try to connect to client through toad i m getting this erorr . however i m ok with connction with database i recently installed and aslo can connect to client using sql and oem. how do configure the sql*Net?

to configure sql* Net for toad follow the steps what i mentioned before.

else copy the tnsnames.ora file from old oracle home to new oracle personal database home

generally u will fine tnsnames.ora file in $ORACLE_HOME\network\admin or $ORACLE_HOME\net80\admin

nagendra gupta

Is your Oracle client in a different Oracle_home than your Personal Oracle database?

You said that you are "ok with connection with database", but which database: Personal Oracle, or another Oracle database on a server?

You said that you can also "connect to client using sql and oem".  This puzzles me.  SQL*Plus and OEM are clients that connect to a database.  They don't connect to a client, they are the client.  Which database do they connect to: Personal Oracle, or another Oracle database on a server?