Resize Redo log for RAC

In RAC, you have seperate log groups for each instance (called threads). You can see which group belongs to which thread by querying v$log. When you add new loggroups, you specify which thread it should belong to. The syntax is

ALTER DATABASE ADD LOGFILE THREAD 1 GROUP 5 ('firstlocation','secondlocation') SIZE 1280M;

SQL> select instance_number, instance_name, thread# from gv$instance;
Show Instance with thread ID

SQL> select group#, thread#, members ,status from v$log;

Check number groups in each of thread.

On RAC, you have to add redo log Group each of node (each of thread )

SQL> select group#, thread#, members ,status from v$log;

From your environment ,I think you have 2 nodes = 2 thread
If these're thread 1, 2
So, add redo group should:

Example:
ALTER DATABASE ADD LOGFILE THREAD 1 GROUP 11 ( '+DATA','+DATA') SIZE 300M,
                                    GROUP 12 ( '+DATA','+DATA') SIZE 300M reuse;
ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 13 ( '+DATA','+DATA') SIZE 300M,
                                    GROUP 14 ( '+DATA','+DATA') SIZE 300M reuse;

You should check each thread has >= 2 groups and that group had "INACTIVE" status before drop:
SQL> select group#, thread#, members ,status from v$log;

now run "alter system switch logfile;ALTER SYSTEM CHECKPOINT GLOBAL;" on all instances:
alter database drop logfile group 1 ,group 2,group 3,group 4,group 5,group 6;


remove the actuall files (GROUP 1-6) from the ASM:
export ORACLE_HOME=/u01/app/oracle/product/10.2.0/asm
export PATH=$ORACLE_HOME/bin:$PATH
export ORACLE_SID=+ASM2
sqlplus /nolog
connect / as sysdba
ALTER DISKGROUP REDOA DROP FILE '+REDOA/dbname/redo01.log';
ALTER DISKGROUP REDOA DROP FILE '+REDOA/dbname/redo02.log';
ALTER DISKGROUP REDOA DROP FILE '+REDOA/dbname/redo05.log';
ALTER DISKGROUP REDOA DROP FILE '+REDOA/dbname/redo06.log';
ALTER DISKGROUP REDOA DROP FILE '+REDOA/dbname/redo03.log';
ALTER DISKGROUP REDOA DROP FILE '+REDOA/dbname/redo04.log';
exit

verify files were removed
##

asmcmd
ASMCMD> cd REDOA
ASMCMD> find . *
+REDOA/DBNAME/
+REDOA/DBNAME/CONTROLFILE/
+REDOA/DBNAME/CONTROLFILE/Current.256.666981619
+REDOA/DBNAME/ONLINELOG/
+REDOA/DBNAME/ONLINELOG/group_10.271.667595443
+REDOA/DBNAME/ONLINELOG/group_20.272.667595443
+REDOA/DBNAME/ONLINELOG/group_30.265.667595411
+REDOA/DBNAME/ONLINELOG/group_40.266.667595411
+REDOA/DBNAME/ONLINELOG/group_50.267.667595411
+REDOA/DBNAME/ONLINELOG/group_60.268.667595411
+REDOA/DBNAME/ONLINELOG/group_70.269.667595413
+REDOA/DBNAME/ONLINELOG/group_80.270.667595413
+REDOA/DBNAME/control01.ctl
+REDOA/DBNAME/redo01-tmp.log
+REDOA/DBNAME/redo02-tmp.log
+REDOA/DBNAME/redo03-tmp.log
+REDOA/DBNAME/redo04-tmp.log
+REDOA/DBNAME/redo05-tmp.log
+REDOA/DBNAME/redo06-tmp.log
+REDOA/DBNAME/redo07-tmp.log
+REDOA/DBNAME/redo08-tmp.log
ASMCMD> exit

now re-create it with "dual" members and bigger size:
ALTER DATABASE ADD LOGFILE THREAD 1 GROUP 1 ( '+DATA','+DATA') SIZE 300M,
                                    GROUP 2 ( '+DATA','+DATA') SIZE 300M,
                                    GROUP 3 ( '+DATA','+DATA') SIZE 300M reuse;
ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 4 ( '+DATA','+DATA') SIZE 300M,
                                    GROUP 5 ( '+DATA','+DATA') SIZE 300M,
                                    GROUP 6 ( '+DATA','+DATA') SIZE 300M reuse;
alter database drop logfile group 11, group 12, group 13, group 14;