How to increase SGA_MAX_SIZE, SGA_TARGET and PGA_AGGREGATE_TARGET in Oracle 11g

SQL> show parameter sga

NAME     TYPE VALUE

------------------------------------ ----------- ------------------------------

lock_sga     boolean FALSE

pre_page_sga     boolean FALSE

sga_max_size     big integer 2G

sga_target     big integer 2G

SQL> ALTER system SET sga_max_size=4G scope=spfile;

System altered.

SQL> ALTER system SET sga_target=4G scope=spfile;

System altered.

---------------------------------------------------------------------------------------------------------------

SQL> show parameter pga

NAME     TYPE VALUE

------------------------------------ ----------- ------------------------------

pga_aggregate_target     big integer 3G

SQL> alter system set PGA_AGGREGATE_TARGET=4G scope=spfile;

System altered.

***Bounce the database for apply the changes done.

SQL> shutdown immediate

ORA-01109: database not open

Database dismounted.

ORACLE instance shut down.

SQL> startup mount

ORACLE instance started.

Total System Global Area 4275781632 bytes

Fixed Size    2260088 bytes

Variable Size  738198408 bytes

Database Buffers 3523215360 bytes

Redo Buffers   12107776 bytes

Database mounted.

SQL> show parameter sga

NAME     TYPE VALUE

------------------------------------ ----------- ------------------------------

lock_sga     boolean FALSE

pre_page_sga     boolean FALSE

sga_max_size     big integer 4G

sga_target     big integer 4G

SQL> show parameter pga

NAME     TYPE VALUE

------------------------------------ ----------- ------------------------------

pga_aggregate_target     big integer 4G