Error while using oracle client

Question

I agree to all what you have written .But as you said we often have client server co-existing on the same hardware platform and also i have additionally installed an oracle client .I agree that the TCP connections is via Net8 (Sql*Net) /ODBC etc. But my question is i want to connect to both my XE server and my other database servers (Production) using a single client (since m having 2 clients , one that came along with the XE database and the other which i have explicitly installed) ,I get the following error
SP2-0667: Message file sp1<lang>.msb not found
SP2-0750: You may need to set ORACLE_HOME to your Oracle software directory .Despite setting the path and ORACLE_HOME environment variables , the error persists.

Answer 1

Windows host? Which version, xp? Which "2nd client" version, instant client?
Double check the environment variables and %PATH%. Try changing directory to the particular client .../bin directory and run sqlplus from there, the client program you want may not be the client program you're getting.
%ORACLE_HOME% also needs to be pre-pended to %PATH%, with that second client it might be helpful to set up a .bat file with proper settings. Saves having to retype stuff which will also be typo-prone, i.e. in ct2.bat:
set ORACLE_HOME=C:\ora\<folder\path>
set PATH=%ORACLE_HOME%;%PATH%