Well it has been over a year since the last time I broke my database, but I did it again today! This time I increased the sga size without also increasing some other parameter, and the database would not start, and since it would not start, I could not change the parameter. What to do?
After a bit of hacking the SPFILE to no avail, I worked out the following process:
First, log on to Oracle as an administrator:
sqlplus / as sysdba
Next, create a nice editable plain text PFILE from the “binary” SPFILE:
create pfile from spfile; exit
Now you can edit PFILE to change whatever parameters you need to. Once you are done, you can start up the database from the PFILE:
sqlplus / as sysdba startup pfile=initSID.ora