How do I change the redo log buffer size, the shared pool size and the database buffer pool size? I know its all in the init.ora file, but what exactly do I change? Also how can I then check to see if my changes actually worked. I mean how can I display the new values?
What version of Oracle are you using?
If you are using Oracle9i, and you are using a server parameter file (spfile), you modify these parameters via ALTER SYSTEM statements. Some, such as DB_CACHE_SIZE and SHARED_POOL_SIZE, can be changed dynamically, i.e., new values will take effect immediately. LOG_BUFFER_SIZE, among others, is a static parameter, which means that you will have to shut down and restart the instance for the change to take effect. See the documentation for ALTER SYSTEM to get the correct syntax.
To verify that the changes have taken place, you can use the SQL*Plus command "show parameter" (e.g. "show parameter log_buffer_size"), or query the v$parameter dynamic performance view.