This parameter allows you to specify the amount of the database heap (defined by the dbheap parameter) to use as a buffer for log records before writing these records to disk.
This parameter must also be less than or equal to the dbheap parameter. Buffering the log records will result in more efficient logging file I/O because the log records will be written to disk less frequently and more log records will be written at each time.
Recommendation: Increase the size of this buffer area if there is considerable read activity on a dedicated log disk, or there is high disk utilization. When increasing the value of this parameter, you should also consider the dbheap parameter since the log buffer area uses space controlled by the dbheap parameter.
You can use the database system monitor to determine how much of the log buffer space is used for a particular transaction (or unit of work). Refer to the log_space_used (unit of work log space used) monitor element.