The Ora-3113 is maybe because the database has not been cleanly shut down yet. Did you try:
Reset the init.ora params to what they were before you did anything.
email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Chirag DBA
Sent: Wednesday, October 05, 2005 1:25 PM
To: R J Zijlstra
Cc: Oracle-L Freelists
Subject: Re: ora- 600 and ora -03113
This error has started from last night and DB is being shutdown for cold backup.
We got 600 at night only, while shutting down the DB. (through scripts).
and today morning users started complaining abt the performance and I changed the SGA.
I put db_block_buffers too hight for sure.
I get ora-600 only then and not after that. Right now we are getting 0ra-03113.
hopefully making db_block_buffers will help.
regards - chirag
On 10/5/05, R J Zijlstra <email@example.com> wrote:
I changed my SGA size from 300mb to 1.5GB.
Users are getting ora-03113 end-of-file comminication channed.
Got this error after starting the Database. It is 220.127.116.11 on solaris.
internal or fatal error
ORA-00600: internal error code, arguments: , , , , , , , 
ORA-01089: immediate shutdown in progress - no operations are permitted
No current SQL statement being executed.
----- PL/SQL Call Stack -----
object line object
reards - chirag