Hi,
Your Log_checkpoint_intreval should be 122880 instead of 512000.It should be Logfilesize/osblocksize.
2) You can also make log_timeout_intreval=0
If you set the above said values, your log switch should happened based on Log file size. If you are running heay OLTP intensive application, you can encounter 4 log switches per hour. This is good as for as performance issues are concerned.
Regs
Sundar,Oracle DBA, Telesis