Redo log buffer 2228 < 4000 - 2,228 < 4000 redo entries

Hi experts ,

I am getting following error in Oracle ( 11.2.0.3)

When I run sql for redo buffer allocation retries, I get as below

SELECT NAME, VALUE FROM V$SYSSTAT WHERE NAME = 'redo buffer allocation retries';

NAME                                                                  VALUE

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

redo buffer allocation retries                                        74955

Everyday it increases by 200

Current LOG_BUFFER size is 20MB

show parameter LOG_BUFFER;

NAME                                 TYPE        VALUE

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

log_buffer                           integer     19955712

How should I resolve this issue ? by increase LOG_BUFFER size ? How do I calculate optimal size ?