In 9i you donot need the init.ora file at all.
There is this concept of SPFILE(A binary file) through which u can make all the changes to the parameters that were done in the init.ora file.
When u say startup ,by default then SPFILE (Location: $ORACLE_HOME/database/SPFILE<SID>.ora) will be picked.
And yeah as suggested earlier,if you want your init.ora to be picked,then use startup PFILE='<init.ora file NAME>'( with full patch if its not in the $ORACLE_HOME/database/ directory)
Modifying Parameters in SPFILE
The ALTER SYSTEM SET command is used to change the value of instance parameters.
ALTER SYSTEM SET parameter_name = parameter_value
[COMMENT 'text'] [SCOPE = MEMORY|SPFILE|BOTH]
parameter_name: Name of the parameter to be changed
parameter_value: Value the parameter is being changed to
COMMENT: A comment to be added into the SPFILE next to the parameter being altered
SCOPE: Determines if change should be made in memory, SPFILE, or in both areas
MEMORY: Changes the parameter value only in the currently running instance
SPFILE: Changes the parameter value in the SPFILE only
BOTH: Changes the parameter value in the currently running instance and the SPFILE
SID: Identifies the ORACLE_SID for the SPFILE being used
'sid': Specific SID to be used in altering the SPFILE
'*': Uses the default SPFILE
ex: ALTER SYSTEM SET undo_tablespace = UNDO2 SCOPE=BOTH;
Adding to the previous update ,please check the values ISSES_MODIFIABLEand ISSYS_MODIFIABLE from V$PARAMETER for the parameters that you want to change.If the values are FALSE,you can update only in the SPFILE using the option scope=SPFILE.Then these changes become effective only when u bounce the DB.
Please note that you should login as SYSDBA to make changes in the SPFILE.