LOG_BUFFER

Parameter type	Integer
Default value	512 KB or 128 KB * CPU_COUNT, whichever is greater
Parameter class	Static
Range of values	Operating system-dependent

LOG_BUFFER specifies the amount of memory (in bytes) that Oracle uses when buffering redo entries to a redo log file. Redo log entries contain a record of the changes that have been made to the database block buffers. The LGWR process writes redo log entries from the log buffer to a redo log file.

In general, larger values for LOG_BUFFER reduce redo log file I/O, particularly if transactions are long or numerous. In a busy system, a value 65536 or higher is reasonable.