The default value for size of the redo log buffer is operating system-specific, but, for most systems, it is 500Kb. If buffer size is increased, the frequency of I/O operations is reduced, and the performance of the Oracle server is increased.
If the log buffer is too small, the log writer process is excessively busy. In this case, the log writer process is constantly writing to disk and may not have enough space for its redo entries. You are more likely to encounter problems with buffers that are too small than with buffers that are too large.
To set the redo log buffer size manually, you must configure the log_buffer initialization parameter of the init.ora file. A size between 1MB and 7MB is optimal.