Memory usage for AMM RAC database and changing RAC database to ASMM

SQL> select sum(bytes/1024/1024) Current_SGA_SIZE_in_MB from v$sgastat;
CURRENT_SGA_SIZE_IN_MB
----------------------
        1804.448437
SQL> select sum(bytes/1024/1024) MAX_SGA_SIZE_in_MB from  v$sgainfo    where name = 'Maximum SGA Size';
MAX_SGA_SIZE_IN_MB
------------------
    2592.84766
SQL> show parameter memory_max_target;
NAME                     TYPE     VALUE
------------------------------------ ----------- ------------------------------
memory_max_target             big integer 1600M
SQL> select (value/1024/1024) Current_PGA_IN_USE_in_MB from v$pgastat where name = 'total PGA inuse';
CURRENT_PGA_IN_USE_IN_MB
------------------------
          788.078938
SQL> select (value/1024/1024) MAX_PGA_ALLOCATED_in_MB from v$pgastat where name = 'maximum PGA allocated';
MAX_PGA_ALLOCATED_IN_MB
-----------------------
         1567.658203
SQL> select (value/1024/1024) PGA_TARGET_in_MB    from v$pgastat where name = 'aggregate PGA target parameter';
PGA_TARGET_IN_MB
----------------
         480





Memory usage of exisitng AMM: 
 - memory reserved  for PGA/SGA: 8 GB 
 - current PGA size 790 MB
 - current SGA size 1804 MB
 - free memory for future PGA/SGA usage: ~ 2.5 GB

For switching ASMM this can be translated into 
  SGA_MAX_SIZE             : 3 GB
  SGA_TARGET               : 3 GB
  PGA_AGGREGATE_TARGET     :  2 GB

For further tuning check : V$PGA_TARGET_ADVICE

Execute the  following commands.
Disable AMM
  SQL> alter system reset memory_max_target scope=spfile  sid='*';
  SQL> alter system reset memory_target  scope=spfile  sid='*';

Enable ASMM
  SQL> alter system set SGA_MAX_SIZE=3G scope=spfile  sid='*';
  SQL> alter system set SGA_TARGET=3G scope=spfile  sid='*'; 
  SQL> alter system set PGA_AGGREGATE_TARGET=2G scope=spfile  sid='*';  

Reboot database and verify that we have switched from AMM to ASMM
SQL> show parameter memory
NAME                     TYPE     VALUE
------------------------------------ ----------- ------------------------------
memory_max_target             big integer 0
memory_target                 big integer 0
--> AMM disabled 

SQL> show parameter sga
NAME                     TYPE          VALUE
------------------------ ----------- ------------------------------
sga_max_size             big integer 3G
sga_target               big integer 3G

SQL> show parameter pga
NAME                     TYPE     VALUE
------------------------ ----------- ------------------------------
pga_aggregate_target     big integer 2G

--> ASMM enabled !