The size of the redo log files can influence performance, because the behavior. of the DBWR and ARCH process depend on the redo log sizes. Generally, larger
redo log files provide better performance. Undersized log files increase checkpoint activity and reduce performance.

Although the size of the redo log files does not affect LGWR performance, it can affect DBWR and checkpoint behavior(Especially related to the switch logfile). Checkpoint frequency is affected by several factors,including log file size and the setting of the FAST_START_MTTR_TARGET initialization parameter. If the FAST_START_MTTR_TARGET parameter is set to limit the instance recovery time, Oracle automatically tries to checkpoint as frequently as necessary.

SQL> show parameter fast_start_mttr_target;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
fast_start_mttr_target               integer     0

SQL> alter system set fast_start_mttr_target=3000 scope=both;

Under this condition, the size of the log files should be large enough to avoid
additional checkpointing due to under sized log files. The optimal size can be obtained by querying the  OPTIMAL_LOGFILE_SIZE  column from the V$INSTANCE_RECOVERY view. You can also obtain sizing advice on the Redo Log Groups page of Oracle Enterprise Manager Database Control.

SQL> select optimal_logfile_size from v$instance_recovery;

OPTIMAL_LOGFILE_SIZE
--------------------
                 686

OPTIMAL_LOGFILE_SIZE NUMBER Redo log file size (in megabytes) that is considered optimal based on the current setting of FAST_START_MTTR_TARGET. It is recommended that,the user configure all online redo logs to be at least this value.

It may not always be possible to provide a specific size recommendation for redo logfiles, but redo log files in the range of a hundred megabytes to a few gigabytes are considered reasonable. Size your online redo log files according to the amount of redo your system generates. A rough guide is to switch logs at most once every twenty minutes.