问题现象：
DG搭建完成后，主库归档不能自动同步到备库。
问题排查：
主库告警日志报错：
PING[ARC2]: Heartbeat failed to connect to standby 'cjcdb02'. Error is 16058.
报错原因：
备库故障，主库无法连接备库，备库恢复后，主库没有尝试重连备库。
解决方案：
主库重新激活log_archive_dest_state_2
过程如下：
主库：
切换归档
SQL> alter system switch logfile ; System altered. SQL> archive log list; Database log mode Archive Mode Automatic archival Enabled Archive destination /arch Oldest online log sequence 15 Next log sequence to archive 17 Current log sequence 17
备库：
没有接收到归档日志
SQL> archive log list; Database log mode Archive Mode Automatic archival Enabled Archive destination /arch Oldest online log sequence 0 Next log sequence to archive 0 Current log sequence 0
查看备库告警日志，没有报错，RFS进程已经启动
RFS connections are allowed
主库：
主库告警日志：
Use the following SQL commands on the standby database to create standby redo logfiles that match the primary database: ALTER DATABASE ADD STANDBY LOGFILE 'srl1.f' SIZE 52428800; ALTER DATABASE ADD STANDBY LOGFILE 'srl2.f' SIZE 52428800; ALTER DATABASE ADD STANDBY LOGFILE 'srl3.f' SIZE 52428800; ALTER DATABASE ADD STANDBY LOGFILE 'srl4.f' SIZE 52428800; Tue Aug 04 15:29:26 2020 ALTER SYSTEM SET log_archive_dest_state_2='ENABLE' SCOPE=MEMORY SID='*'; Tue Aug 04 15:29:26 2020 PING[ARC2]: Heartbeat failed to connect to standby 'cjcdb02'. Error is 16058. Tue Aug 04 15:29:28 2020
主库连接一次备库失败后，没有尝试重连。
主库：
重新激活
SQL> alter system set log_archive_dest_state_2=defer; SQL> alter system set log_archive_dest_state_2=enable;
主库告警日志：
Tue Aug 04 15:33:58 2020 ALTER SYSTEM SET log_archive_dest_state_2='DEFER' SCOPE=BOTH; Tue Aug 04 15:34:22 2020 ALTER SYSTEM SET log_archive_dest_state_2='ENABLE' SCOPE=BOTH; Tue Aug 04 15:34:22 2020 Thread 1 cannot allocate new log, sequence 20 Checkpoint not complete Current log# 1 seq# 19 mem# 0: /oracle/oradata/cjcdb01/redo01.log Thread 1 cannot allocate new log, sequence 20 Private strand flush not complete Current log# 1 seq# 19 mem# 0: /oracle/oradata/cjcdb01/redo01.log Thread 1 advanced to log sequence 20 (LGWR switch) Current log# 2 seq# 20 mem# 0: /oracle/oradata/cjcdb01/redo02.log Tue Aug 04 15:34:29 2020 Archived Log entry 17 added for thread 1 sequence 19 ID 0x3995c964 dest 1: Tue Aug 04 15:34:29 2020 ARC0: Standby redo logfile selected for thread 1 sequence 19 for destination LOG_ARCHIVE_DEST_2 Tue Aug 04 15:34:29 2020 ****************************************************************** LGWR: Setting 'active' archival for destination LOG_ARCHIVE_DEST_2 ****************************************************************** LNS: Standby redo logfile selected for thread 1 sequence 20 for destination LOG_ARCHIVE_DEST_2
备库告警日志：
Tue Aug 04 15:34:21 2020 RFS[1]: Assigned to RFS process 11502 RFS[1]: Opened log for thread 1 sequence 14 dbid 966115684 branch 1047470758 Tue Aug 04 15:34:21 2020 RFS[2]: Assigned to RFS process 11504 RFS[2]: Opened log for thread 1 sequence 16 dbid 966115684 branch 1047470758 Tue Aug 04 15:34:21 2020 RFS[3]: Assigned to RFS process 11506 RFS[3]: Opened log for thread 1 sequence 15 dbid 966115684 branch 1047470758 Archived Log entry 1 added for thread 1 sequence 14 rlc 1047470758 ID 0x3995c964 dest 2: RFS[1]: Opened log for thread 1 sequence 17 dbid 966115684 branch 1047470758 Archived Log entry 2 added for thread 1 sequence 16 rlc 1047470758 ID 0x3995c964 dest 2: Archived Log entry 3 added for thread 1 sequence 17 rlc 1047470758 ID 0x3995c964 dest 2: Archived Log entry 4 added for thread 1 sequence 15 rlc 1047470758 ID 0x3995c964 dest 2: RFS[2]: Opened log for thread 1 sequence 18 dbid 966115684 branch 1047470758 Archived Log entry 5 added for thread 1 sequence 18 rlc 1047470758 ID 0x3995c964 dest 2: RFS[2]: Selected log 4 for thread 1 sequence 19 dbid 966115684 branch 1047470758 Tue Aug 04 15:34:28 2020 Archived Log entry 6 added for thread 1 sequence 19 ID 0x3995c964 dest 1: Tue Aug 04 15:34:28 2020 Primary database is in MAXIMUM PERFORMANCE mode RFS[4]: Assigned to RFS process 11514 RFS[4]: Selected log 4 for thread 1 sequence 20 dbid 966115684 branch 1047470758
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