How to change SGA in Oracle Rac

This Article for newbe Oracle DBA Since If you trying to change sga on rac with wrong way , spfile maybe be corrupted . 

Node One : ORCL1
Node Two : ORCL2

Note : You Need To Check Memory Parameter On Database , if its Have Available Size .

• Connect To Node One :

alter system set sga_max_size=16g scope=spfile sid = 'ORCL1';
alter system set sga_target=12g scope=spfile sid = 'ORCL1';
alter system set sga_max_size=16g scope=spfile sid = 'ORCL2';
alter system set sga_target=12g scope=spfile sid = 'ORCL2';

Or In Another Way :
sql>alter system set sga_target=12G scope=spfile sid=’*’;
sql>alter system set sga_max_size=16G scope=spfile sid=’*’;
sql>alter system set sga_max_size=16G scope=spfile ;
sql>alter system set sga_target=12G scope=spfile;

 PGA :

sql>alter system set pga_aggregate_target=4G scope =spfile sid=’*’;
sql>alter system set pga_aggregate_target=4G scope=both;

• shutdown database PROD (two instances should be shut down)

 $>srvctl stop database -d PROD

$>srvctl START database -d PROD

Check The New Size For Both Instance By :

Show parameter sga ;

Thank you
Osama mustafa