I have two Oracle home in my PC, 8.0.5 and 8.1.7 , connection to Databases from 8.0.5 sqlplus is fine.
I have copied the TNSNAMES.ORA from 8.0.5 network folder to 8.1.7 network\admin folder but still when I am trying to connect to Database by sqlplus version 8.1.7 it returns erro : Could not resolve servica name. I try change Oracle home with home selector also. Didn't help.

Can you elaborate how can I resolve this issue?

Thanks