DataGuard不设置FAL也自动传送丢失的Archive Log，什么原因？

FunBSD

Oracle 9.2.0.8
手册和别人的文档里写的都是要设置FAL_Server和FAL_Client
但我试验了一下，不设置这两个参数，一样自动传送丢失的Archive Log

standby日志显示不能获取gap sequence，但是primary自动传送了gap sequence之后，standby自动继续恢复过程。

standby日志：
Media Recovery Log /opt/oracle/oradata/oradb1/archive/1_163.dbf
Error opening /opt/oracle/oradata/oradb1/archive/1_163.dbf
Attempting refetch
Media Recovery Waiting for thread 1 seq# 163
Fetching gap sequence for thread 1, gap sequence 163-163
Trying FAL server:
Error fetching gap sequence, no FAL server specified
Wed Mar 24 13:22:24 2010
Failed to request gap sequence. Thread #: 1, gap sequence: 163-163
All FAL server has been attempted.
Media Recovery Log /opt/oracle/oradata/arch/1_163.dbf
Media Recovery Log /opt/oracle/oradata/arch/1_164.dbf
......

primary日志：
Wed Mar 24 13:22:55 2010
ARC1: Begin FAL archive (thread 1 sequence 163 destination ORADB_STANDBY)
Creating archive destination LOG_ARCHIVE_DEST_2: 'ORADB_STANDBY'
ARC1: Complete FAL archive (thread 1 sequence 163 destination ORADB_STANDBY)

FunBSD

以下是我的想法，不知道对不对

设置了FAL_Server和FAL_Client，就会在standby上pull archive log
设置了FAL_Server和FAL_Client，还可以从其他服务器上pull archive log，不一定是从primary上

如果不设置FAL_Server和FAL_Client，那就自动从primary向standby push arvhice log