Can't connect to Oracle after running alter statement

Alter system set Processes=2 SCOPE=SPFILE;

ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist

You will need more than two processes, so setting the PROCESS parameter this low is causing your problems. Remember that PMON, SMON and all of the other background processes count against the total number of processes running in the system. Oracle 9.2 requires at least five processes in order for the instance to stay up and running. And then you'll want users to be able to connect to your instance, which are more processes.

You need to modify your SPFILE's contents. Unfortunately, you cannot start the instance. So try this little trick:

1. STARTUP NOMOUNT the instance
2. CREATE PFILE FROM SPFILE;
3. Using a text editor, modify the pfile to have more than two processes. The pfile will be in the default location.
4. CREATE SPFILE FROM PFILE;
5. ALTER DATABASE OPEN;

Using the above method, you can always modify the SPFILE's contents when you need to and the instance won't open.