REDO LOG BUFFER

Hi everyone,
My database is 10.2.0.5.0 standard edition having running on windows server 2008 32-bit.
My database is showing these statistic,GOOGLE told me increase the size of redo log buffer:-

SQL>   SELECT name, value FROM SYS.v_$sysstat
  2       WHERE NAME in ('redo buffer allocation retries','redo wastage',
  3                      'redo log space wait time','redo log space requests');

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo buffer allocation retries                                         1251
redo wastage                                                       49103144
redo log space requests                                                 348
redo log space wait time                                               4473

my SGA is:-
SQL> sho sga

Total System Global Area  612368384 bytes
Fixed Size                  1304752 bytes
Variable Size             171968336 bytes
Database Buffers          436207616 bytes
Redo Buffers                2887680 bytes

plz help me,should i need to increase the size of redo log buffer only or i need to increase the size of SGA.