Scopes when running with Pfile

SQL> create pfile from spfile;

SQL> shut immediate

oracle> cd $ORACLE_HOME/dbs

oracle> mv spfilessss.ora spfilessss.ora.bkp

oracle> export ORACLE_SID=ssss

oracle> sqlplus / as sysdba

SQL> startup

SQL> show parameter pfile;

SQL> show parameter undo_

SQL> alter system set undo_retention=900 scope=memory;

                If we wont specify the scope for dynamic parameter when running with pfile, it take "memory" by default.

                "memory" means it is applicable for current.

SQL> show parameter undo_