DG切换时有GAP的解决！

DG在主库切换为备库后，又切换回来时（原来的主库还是主库）时，
在主库上执行SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;
时，长时间没有影响。
日志文件中如下：

Media Recovery Waiting for thread 1 seq# 115
Fetching gap sequence for thread 1, gap sequence 115-116
Trying FAL server: PRIMARYDB
Wed May 14 08:52:58 2008
Completed: alter database recover managed standby database di
Wed May 14 08:53:12 2008
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY
Wed May 14 08:53:12 2008
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY
Wed May 14 08:53:12 2008
Failed to request gap sequence. Thread #: 1, gap sequence: 115-116
All FAL server has been attempted.
Wed May 14 09:00:57 2008
ALTER SYSTEM SET fal_server='STANDBYDB' SCOPE=BOTH;
Wed May 14 09:01:23 2008
ALTER SYSTEM SET fal_client='PRIMARYDB' SCOPE=BOTH;
Wed May 14 09:13:42 2008
显示LOG有Gap，需要有sequence: 115-116

SQL> select * from v$archive_gap;

   THREAD# LOW_SEQUENCE# HIGH_SEQUENCE#
---------- ------------- --------------
         1           115            116
手动COPY，LOG:115,116
之后REGISTEER,问题解决。

SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE

'E:\oracle\oradata\TSTDB\standbyAr
ch\ARC00115.001';

数据库已更改。

SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE

'E:\oracle\oradata\TSTDB\standbyAr
ch\ARC00116.001';

数据库已更改。

ALTER中如下：

ALTER DATABASE REGISTER PHYSICAL LOGFILE

'E:\oracle\oradata\TSTDB\standbyArch\ARC00115.001'
Wed May 14 09:13:42 2008
There are 1 logfiles specified.
ALTER DATABASE REGISTER [PHYSICAL] LOGFILE
Completed: ALTER DATABASE REGISTER PHYSICAL LOGFILE 'E:\oracl
Wed May 14 09:13:45 2008
Media Recovery Log E:\ORACLE\ORADATA\TSTDB\STANDBYARCH\ARC00115.001
Media Recovery Waiting for thread 1 seq# 116
Fetching gap sequence for thread 1, gap sequence 116-116
Trying FAL server: STANDBYDB
Wed May 14 09:13:49 2008
ALTER DATABASE REGISTER PHYSICAL LOGFILE

'E:\oracle\oradata\TSTDB\standbyArch\ARC00116.001'
Wed May 14 09:13:49 2008
There are 1 logfiles specified.
ALTER DATABASE REGISTER [PHYSICAL] LOGFILE
Completed: ALTER DATABASE REGISTER PHYSICAL LOGFILE 'E:\oracl
Wed May 14 09:14:01 2008
Media Recovery Log E:\ORACLE\ORADATA\TSTDB\STANDBYARCH\ARC00116.001
Media Recovery Log E:\ORACLE\ORADATA\TSTDB\STANDBYARCH\ARC00117.001
Media Recovery Log E:\ORACLE\ORADATA\TSTDB\STANDBYARCH\ARC00118.001
Media Recovery Log E:\ORACLE\ORADATA\TSTDB\STANDBYARCH\ARC00119.001
Media Recovery Log E:\ORACLE\ORADATA\TSTDB\STANDBYARCH\ARC00120.001
Identified end-of-REDO for thread 1 sequence 120
Identified end-of-REDO for thread 1 sequence 120
Media Recovery End-Of-Redo indicator encountered
Media Recovery Applied until change 5484035
MRP0: Media Recovery Complete: End-Of-REDO
Resetting standby activation ID 3188455604 (0xbe0bf8b4)
MRP0: Background Media Recovery process shutdown
Wed May 14 09:14:03 2008
RESETLOGS after incomplete recovery UNTIL CHANGE 5484035
Resetting resetlogs activation ID 0 (0x0)
Wed May 14 09:14:17 2008
Online log 4 of thread 0 was previously cleared
Online log 5 of thread 0 was previously cleared
Online log 6 of thread 0 was previously cleared
Online log 7 of thread 0 was previously cleared
Switchover: Complete - Database shutdown required
Completed: ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY