I upgraded a 8i database to 10g using DBUA and it showed the upgrade was successful. Now I can access the database using SQL*Plus on the server. However, when I tried to access the database from a 10g client using SQL*Plus, it gave the following errors:

ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
SVR4 Error: 2: No such file or directory

I am not familiar with 10g. Does anyone know what could be wrong? Thanks a lot!