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数据库管理-第244期 一次无法switchover的故障处理（20240928）

作者：胖头鱼的鱼缸（尹海文）
Oracle ACE Pro: Database（Oracle与MySQL）
PostgreSQL ACE Partner
10年数据库行业经验，现主要从事数据库服务工作
拥有OCM 11g/12c/19c、MySQL 8.0 OCP、Exadata、CDP等认证
墨天轮MVP、年度墨力之星，ITPUB认证专家、专家百人团成员，OCM讲师，PolarDB开源社区技术顾问，HaloDB外聘技术顾问，OceanBase观察团成员，青学会MOP技术社区（青年数据库学习互助会）技术顾问
圈内拥有“总监”、“保安”、“国产数据库最大敌人”等称号，非著名社恐（社交恐怖分子）
公众号：胖头鱼的鱼缸；CSDN：胖头鱼的鱼缸（尹海文）；墨天轮：胖头鱼的鱼缸；ITPUB：yhw1809。
除授权转载并标明出处外，均为“非法”抄袭

中秋前做了一次数据库的倒换演练，结果发现无法switchover，本期就来跟随总监一步一步的寻找并解决问题（同时感谢SR支持）。

1 问题展现

在DGMGRL中进行switchover的时候出现了下面的问题：

DGMGRL> switchover to dbdg;
Performing switchover NOW, please wait...
Error: ORA-16775: target standby database in broker operation has potential data lossFailed.
Unable to switchover, primary database is still "dbaas"

2 问题排查与处理

2.1 问题1

第一个问题呢是在DGMGRL中show configuration:

DGMGRL> show configurationConfiguration - dgProtection Mode: MaxPerformanceMembers:dbaas - Primary databasedbdg - Physical standby databaseError: ORA-16664: unable to receive the result from a memberFast-Start Failover: DisabledConfiguration Status:
ERROR (status updated 34 seconds ago)

但是使用show configuration verbose则是显示正常，查看主备库也是正常的：

DGMGRL> show configuration verboseConfiguration - dgProtection Mode: MaxPerformanceMembers:dbaas - Primary databasedbdg  - Physical standby database Properties:FastStartFailoverThreshold      = '30'OperationTimeout                = '30'TraceLevel                      = 'SUPPORT'FastStartFailoverLagLimit       = '30'CommunicationTimeout            = '180'ObserverReconnect               = '0'FastStartFailoverAutoReinstate  = 'TRUE'FastStartFailoverPmyShutdown    = 'TRUE'BystandersFollowRoleChange      = 'ALL'ObserverOverride                = 'FALSE'ExternalDestination1            = ''ExternalDestination2            = ''PrimaryLostWriteAction          = 'CONTINUE'ConfigurationWideServiceName    = 'dbaas_CFG'Fast-Start Failover:  DisabledConfiguration Status:
SUCCESSDGMGRL> show database dbaasDatabase - dbaasRole:               PRIMARYIntended State:     TRANSPORT-ONInstance(s):dbaas1dbaas2Database Status:
SUCCESSDGMGRL> show database dbdg
Database - dbdgRole:               PHYSICAL STANDBYIntended State:     APPLY-ONTransport Lag:      0 seconds (computed 0 seconds ago)Apply Lag:          0 seconds (computed 0 seconds ago)Average Apply Rate: 61.30 MByte/sReal Time Query:    ONInstance(s):dbdg1dbdg2 (apply instance)dbdg3dbdg4Database Status:
SUCCESS

最终发现是数据库本身是配置了db_domain的，而tnsname和静态监听中未配置domain（即域名后缀，如xxx.com），随机调整监听和tnsname：
监听调整（以主库实例1和listener_scan1为例）：

SID_LIST_LISTENER =(SID_LIST =(SID_DESC =(GLOBAL_DBNAME = dbaas.scmcc.com) #增加domain(ORACLE_HOME = /u01/app/oracle/product/19.0.0.0/dbhome_1)(SID_NAME = dbaas1))(SID_DESC =(GLOBAL_DBNAME = dbaas_DGMGRL.scmcc.com) #增加domain(ORACLE_HOME = /u01/app/oracle/product/19.0.0.0/dbhome_1)(SID_NAME = dbaas1)))
SID_LIST_LISTENER_SCAN1 =(SID_LIST =(SID_DESC =(GLOBAL_DBNAME =dbaas.scmcc.com) #增加domain(ORACLE_HOME = /u01/app/oracle/product/19.0.0.0/dbhome_1)(SID_NAME = dbaas1))(SID_DESC =(GLOBAL_DBNAME = dbaas_DGMGRL.scmcc.com) #增加domain(ORACLE_HOME = /u01/app/oracle/product/19.0.0.0/dbhome_1)(SID_NAME = dbaas1)))

完成后reload所有监听。
tnsname调整：

DBAAS =(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = primary-scan)(PORT = 1521))(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = dbaas.xxx.com) #增加domain))DBDG =(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = standby-scan)(PORT = 1521))(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = dbdg.xxx.com) #增加domain))

完成后show configuration恢复正常：

DGMGRL> show configurationConfiguration - dgProtection Mode: MaxPerformanceMembers:dbaas - Primary databasedbdg  - Physical standby database Fast-Start Failover:  DisabledConfiguration Status:
SUCCESS   (status updated 59 seconds ago)

2.2 问题2

接下来尝试switchover报错依然，validate备库发现一些问题：

DGMGRL> validate database verbose dbdgDatabase Role:     Physical standby databasePrimary Database:  dbaasReady for Switchover:  No #<---HereReady for Failover:    Yes (Primary Running)Flashback Database Status:dbaas:  Offdbdg :  OffCapacity Information:Database  Instances        Threads        dbaas   2                4              dbdg    4                4              Managed by Clusterware:dbaas:  YES            dbdg :  YES            Temporary Tablespace File Information:dbaas TEMP Files:  56dbdg TEMP Files:   67Data file Online Move in Progress:dbaas:  Nodbdg:   NoStandby Apply-Related Information:Apply State:      RunningApply Lag:        0 seconds (computed 0 seconds ago)Apply Delay:      0 minutesTransport-Related Information:Transport On:  YesGap Status:    Gap #<---HereTransport Lag:  0 seconds (computed 0 seconds ago)Transport Status:  SuccessLog Files Cleared:dbaas Standby Redo Log Files:  Cleareddbdg Online Redo Log Files:    Cleareddbdg Standby Redo Log Files:   AvailableCurrent Log File Groups Configuration:Thread #  Online Redo Log Groups  Standby Redo Log Groups Status       (dbaas)                 (dbdg)                             2         4                       7                       Sufficient SRLs1         4                       7                       Sufficient SRLs3         4                       7                       Sufficient SRLs4         4                       7                       Sufficient SRLsFuture Log File Groups Configuration:Thread #  Online Redo Log Groups  Standby Redo Log Groups Status       (dbdg)                  (dbaas)                            2         4                       7                       Sufficient SRLs1         4                       7                       Sufficient SRLs3         4                       7                       Sufficient SRLs4         4                       7                       Sufficient SRLsCurrent Configuration Log File Sizes:Thread #   Smallest Online Redo      Smallest Standby Redo    Log File Size             Log File Size            (dbaas)                   (dbdg)                 2          2048 MBytes               2048 MBytes              1          2048 MBytes               2048 MBytes              3          2048 MBytes               2048 MBytes              4          2048 MBytes               2048 MBytes              Future Configuration Log File Sizes:Thread #   Smallest Online Redo      Smallest Standby Redo    Log File Size             Log File Size            (dbdg)                    (dbaas)                2          2048 MBytes               2048 MBytes              1          2048 MBytes               2048 MBytes              3          2048 MBytes               2048 MBytes              4          2048 MBytes               2048 MBytes              Apply-Related Property Settings:Property                        dbaas Value              dbdg ValueDelayMins                       0                        0ApplyParallel                   AUTO                     AUTOApplyInstances                  0                        0Transport-Related Property Settings:Property                        dbaas Value              dbdg ValueLogShipping                     ON                       ONLogXptMode                      sync                     syncDependency                      <empty>                  <empty>DelayMins                       0                        0Binding                         optional                 optionalMaxFailure                      0                        0ReopenSecs                      300                      300NetTimeout                      30                       30RedoCompression                 DISABLE                  DISABLE

仍然显示无法switchover且存在GAP，但是通过数据库查询发现并未出现GAP（查询语句如下，结果略）：

-- primary database
set markup HTML on
spool /tmp/primary_info.html
ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';select thread#, max(sequence#) "Last Primary Seq Generated"
from gv$archived_log val, gv$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
group by thread# order by 1;SELECT thread#, dest_id, gvad.status, error, fail_sequence FROM gv$archive_dest gvad, gv$instance gvi WHERE gvad.inst_id = gvi.inst_id AND destination is NOT NULL ORDER BY thread#, dest_id;select * from gv$dataguard_stats;SELECT a.thread#, b. last_seq, a.applied_seq, a. last_app_timestamp, b.last_seq-a.applied_seq ARC_DIFF FROM (SELECT thread#, MAX(sequence#) applied_seq, MAX(next_time) last_app_timestamp FROM gv$archived_log WHERE applied = 'YES' GROUP BY thread#) a, (SELECT thread#, MAX (sequence#) last_seq FROM gv$archived_log GROUP BY thread#) b WHERE a.thread# = b.thread#;spool off
set markup HTML off-- standby database
set markup HTML on
spool /tmp/standby_info.htmlALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';select process,thread#,sequence#,status from gv$managed_standby;select * from v$dataguard_stats;select a.thread#
,a.sequence#
,a.group# grp
, a.bytes/1024/1024 Size_MB
,a.status
,a.archived
,a.first_change# "First SCN Number"
,to_char(FIRST_TIME,'DD-Mon-RR HH24:MI:SS') "First SCN Time"
,to_char(LAST_TIME,'DD-Mon-RR HH24:MI:SS') "Last SCN Time" from
v$standby_log a order by 1,2,3,4;select thread#, max(sequence#) "Last Standby Seq Received"
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
group by thread# order by 1;select thread#, max(sequence#) "Last Standby Seq Applied"
from v$archived_log val, v$database vdb
where val.resetlogs_change# = vdb.resetlogs_change#
and val.applied in ('YES','IN-MEMORY')
group by thread# order by 1;spool off
set markup HTML off

主库检查thread:

SQL> SELECT thread#, instance, status FROM v$thread;THREAD# INSTANCE             STATUS
---------- -------------------- ------1 dbaas1               OPEN2 dbaas2               OPEN3 UNNAMED_INSTANCE_3   CLOSED4 UNNAMED_INSTANCE_4   CLOSED

这里后台建议做了一个操作：

ALTER DATABASE DISABLE THREAD 3;
ALTER DATABASE DISABLE THREAD 4;

运行一段时间后再次validate备库：

DGMGRL> validate database verbose dbdg
...Ready for Switchover:  Yes
...Gap Status:    No Gap
...

显示可以切换且没有Gap了。目前还没有尝试再次switchover，但应该是没问题了。

3 问题分析

这里也是我第一次遇到这个问题，应该是一开始因为domain配置引起的元数据问题。关于thread的问题，因为主备节点数量不一致，但是其他类似配置的库并没有出现过相关问题，所以我怀疑还是和domain配置有问题带来的连锁反应。

4 总结

本期处理了一个ADG无法switchover的问题，源自于最早的错误配置。
老规矩，知道写了些啥。