现象：ADG无法切换：验证时就报错 ORA-16467

(资料图片)

记录问题，顺便展现一次troubleshooting的心路历程。

具体查询：

在主库操作，@primary

切换验证：

alter database switchover to demorac verify;

报错ORA-16467：

SQL> alter database switchover to demorac verify;alter database switchover to demorac verify*ERROR at line 1:ORA-16467: switchover target is not synchronized

主库alert告警日志：

ORA-16467 signalled during: alter database switchover to demorac verify...

主库传输链路并没有报错：

SQL> select error from v$archive_dest where dest_id= 2;ERROR-----------------------------------------------------------------

但是，如果去查v$archive_dest_status，就会发现问题，说有可解决的GAP：

SQL> select dest_id, status, gap_status from v$archive_dest_status where dest_id = 2;   DEST_ID STATUS    GAP_STATUS---------- --------- ------------------------ 2 VALID     RESOLVABLE GAP

但是去备库查询，@standby,

ADG并没有任何延迟：

SQL> select * from v$dataguard_stats;SOURCE_DBID SOURCE_DB_ NAME      VALUE     UNIT    TIME_COMPUTED   DATUM_TIME      CON_ID----------- ---------- ---------------------- ---------------------- ------------------------------ ------------------------------ ------------------------------ ----------  0       transport lag      +00 00:00:00     day(2) to second(0) interval   05/11/2023 18:16:43    05/11/2023 18:16:41   0  0       apply lag      +00 00:00:00     day(2) to second(0) interval   05/11/2023 18:16:43    05/11/2023 18:16:41   0  0       apply finish time     day(2) to second(3) interval   05/11/2023 18:16:43    0  0       estimated startup time 18     second    05/11/2023 18:16:43    0

查MOS文档资料，有一个bug：

Bug 33663444 - DataGuard: "alter database switchover verify" fails with ORA-16467 (Doc ID 33663444.8)

可是很快也排除掉：现象细节不完全匹配，另外这个bug正好在19.16已经修复：

[oracle@bogon ~]$ $ORACLE_HOME/OPatch/opatch lsinventory|grep 33663444     29353271, 29706141, 26352569, 33663444, 30476768, 30092280, 30843271

但这个文档给的一些解释中也得到了一些启发：

REDISCOVERY INFORMATION:  SELECT GAP_STATUS FROM V$ARCHIVE_DEST_STATUS with show unresolvable gap. Workaround  temporarily re-enable the disabled redo thread

首先，我们查V$ARCHIVE_DEST_STATUS已经确认是resolvable gap，不匹配但是也有问题。然后redo thread的re-enable，这个workaround让我去想到查询redo的thread，结果发现果然有些异常：

SQL> select * from v$log;    GROUP#    THREAD#  SEQUENCE#      BYTES  BLOCKSIZE  MEMBERS ARC STATUS       FIRST_CHANGE# FIRST_TIM NEXT_CHANGE# NEXT_TIME  CON_ID---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- --------- ------------ --------- ---------- 1    1    1132  209715200   5121 NO  CURRENT    44911942 11-MAY-23 9.2954E+18       0 2    1    1130  209715200   5121 YES INACTIVE    44901958 11-MAY-23   44911931 11-MAY-23       0 3    1    1131  209715200   5121 YES INACTIVE    44911931 11-MAY-23   44911942 11-MAY-23       0 4    2       0  104857600   5121 YES UNUSED   0  0       0 5    2       0  104857600   5121 YES UNUSED   0  0       0

我这里目前主库是单实例，而备库才是RAC，可是，为何主库的redo居然会有 thread#=2 的redo？虽然都是unused，但出现在这里就很奇怪！不知道谁动了这个环境，想不起来做过这样的测试。但可以肯定的是，完全可以把这个不该存在的thread删除掉！

直接删除会报错：

alter database drop logfile group 4;alter database drop logfile group 5;SQL> alter database drop logfile group 4;alter database drop logfile group 4*ERROR at line 1:ORA-01567: dropping log 4 would leave less than 2 log files for instance UNNAMED_INSTANCE_2 (thread 2)ORA-00312: online log 4 thread 2: "/flash/fast_recovery_area/DEMO/onlinelog/o1_mf_4_kxn73zny_.log"SQL> alter database drop logfile group 5;alter database drop logfile group 5*ERROR at line 1:ORA-01567: dropping log 5 would leave less than 2 log files for instance UNNAMED_INSTANCE_2 (thread 2)ORA-00312: online log 5 thread 2: "/flash/fast_recovery_area/DEMO/onlinelog/o1_mf_5_kxn73zqd_.log"

删除不掉就尝试去先禁用掉这个没有用的thread 2，然后再次尝试删除：alter database disable thread 2;

SQL> alter database disable thread 2;Database altered.SQL> select * from v$log;    GROUP#    THREAD#  SEQUENCE#      BYTES  BLOCKSIZE  MEMBERS ARC STATUS       FIRST_CHANGE# FIRST_TIM NEXT_CHANGE# NEXT_TIME  CON_ID---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- --------- ------------ --------- ---------- 1    1    1132  209715200   5121 NO  CURRENT    44911942 11-MAY-23 9.2954E+18       0 2    1    1130  209715200   5121 YES INACTIVE    44901958 11-MAY-23   44911931 11-MAY-23       0 3    1    1131  209715200   5121 YES INACTIVE    44911931 11-MAY-23   44911942 11-MAY-23       0 4    2       0  104857600   5121 YES UNUSED   0  0       0 5    2       0  104857600   5121 YES UNUSED   0  0       0SQL> alter database drop logfile group 4;Database altered.SQL> alter database drop logfile group 5;Database altered.SQL>SQL>SQL> select * from v$log;    GROUP#    THREAD#  SEQUENCE#      BYTES  BLOCKSIZE  MEMBERS ARC STATUS       FIRST_CHANGE# FIRST_TIM NEXT_CHANGE# NEXT_TIME  CON_ID---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- --------- ------------ --------- ---------- 1    1    1132  209715200   5121 NO  CURRENT    44911942 11-MAY-23 9.2954E+18       0 2    1    1130  209715200   5121 YES INACTIVE    44901958 11-MAY-23   44911931 11-MAY-23       0 3    1    1131  209715200   5121 YES INACTIVE    44911931 11-MAY-23   44911942 11-MAY-23       0

删除成功！这次想来总该可以了吧？

SQL> alter database switchover to demorac verify;alter database switchover to demorac verify*ERROR at line 1:ORA-16467: switchover target is not synchronized

额，还是不行，但感觉再刺激刺激就OK了，继续尝试之前的十八般武艺（主要还是多切几次日志）：

SQL> select dest_id, status, gap_status from v$archive_dest_status where dest_id = 2;   DEST_ID STATUS    GAP_STATUS---------- --------- ------------------------ 2 VALID     RESOLVABLE GAPSQL>SQL> alter system switch logfile;System altered.SQL> select dest_id, status, gap_status from v$archive_dest_status where dest_id = 2;   DEST_ID STATUS    GAP_STATUS---------- --------- ------------------------ 2 VALID     RESOLVABLE GAPSQL> alter system archive log current;System altered.SQL> select dest_id, status, gap_status from v$archive_dest_status where dest_id = 2;   DEST_ID STATUS    GAP_STATUS---------- --------- ------------------------ 2 VALID     RESOLVABLE GAPSQL> alter system switch logfile;alter system switch logfile;System altered.SQL>System altered.SQL>SQL>SQL>SQL> alter system switch logfile;System altered.SQL> select dest_id, status, gap_status from v$archive_dest_status where dest_id = 2;   DEST_ID STATUS    GAP_STATUS---------- --------- ------------------------ 2 VALID     NO GAPSQL>

哎呀，直接提示没有GAP了，赶紧尝试继续切换。。

SQL> alter database switchover to demorac verify;alter database switchover to demorac verify*ERROR at line 1:ORA-16475: succeeded with warnings, check alert log for more detailsSQL> !dateThu May 11 18:36:31 CST 2023

额？成功了，但是有警告，看告警日志又是一个新的ORA-16475 错误。

2023-05-11T18:36:14.906996+08:00alter database switchover to demorac verify2023-05-11T18:36:15.094516+08:00SWITCHOVER VERIFY: Send VERIFY request to switchover target DEMORACSWITCHOVER VERIFY WARNING: switchover target temporary files are not the same with the primary. See switchover target"s alert log for details.ORA-16475 signalled during: alter database switchover to demorac verify...

哎呀，去看看备库的alert日志：

2023-05-11T18:41:29.407685+08:00SWITCHOVER VERIFY BEGINSWITCHOVER VERIFY WARNING: primary database has 5 temporary files, this database has 4 temporary files. More temp files  should be added to this database.SWITCHOVER VERIFY COMPLETE

注意这个时间不太一致是因为两个机器时间不一样（差了5分钟），可以先不用管。看问题本身是说临时文件，这无所谓，切换后可以自动创建。

快快来一把久违的切换吧！

--主库执行成功alter database switchover to demorac;--新主库demoracalter database open;--新备库demostartuprecover managed standby database disconnect;

具体ADG切换参考：

19c ADG Switchover 切换测试

嗯，终于OK了，也感觉肚子饿了，去点餐了。