ORA-27101 shared memory realm does not exist

hello all..

Iam trying to connec to a 9.0.1 database....as a user and this is what i get....
************************************************

ORA-27101 shared memory realm does not exist

****************************************************

What does that mean and how to fix it ?...Increase SGA ?...


Any help is appreciated.

The ORACLE_HOME or ORACLE_SID is not set properly. In previous versions when it is not pointing to the right ORACLE_SID, Oracle used to give an error of ORA-1034 only. Now with 8.1.7 it gives an error of ORA-27101.