环境： Oracle 19.16 ADG (Single Instance -> RAC)
在配置ADG的场景，发现ADG不能同步。
1.查看报错信息
1）主库alert日志：
2023-01-29T11:18:41.489164+08:00
TT00 (PID:27840): Error 12514 received logging on to the standby
TT00 (PID:27840): Attempting LAD:2 network reconnect (12514)
TT00 (PID:27840): LAD:2 network reconnect abandoned
2023-01-29T11:18:41.489623+08:00
Errors in file /u01/app/oracle/diag/rdbms/demo/demo/trace/demo_tt00_27840.trc:
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor
TT00 (PID:27840): krsg_check_connection: Error 12514 connecting to standby 'demorac'
2）ADG配置链路的error信息：
SQL> select error from v$archive_dest where dest_id = 2;
ERROR
-----------------------------------------------------------------
ORA-12514: TNS:listener does not currently know of service
requested in connect descriptor
错误号一致，均为12514。
2.oerr查看该错误说明
[oracle@bogon 2023_01_28]$ oerr ora 12514
12514, 00000, "TNS:listener does not currently know of service requested in connect descriptor"
// *Cause: The listener received a request to establish a connection to a
// database or other service. The connect descriptor received by the listener
// specified a service name for a service (usually a database service)
// that either has not yet dynamically registered with the listener or has
// not been statically configured for the listener. This may be a temporary
// condition such as after the listener has started, but before the database
// instance has registered with the listener.
// *Action:
// - Wait a moment and try to connect a second time.
// - Check which services are currently known by the listener by executing:
// lsnrctl services <listener name>
// - Check that the SERVICE_NAME parameter in the connect descriptor of the
// net service name used specifies a service known by the listener.
// - If an easy connect naming connect identifier was used, check that
// the service name specified is a service known by the listener.
// - Check for an event in the listener.log file.
3.尝试sqlplus连接到standby
[oracle@bogon 2023_01_28]$ sqlplus sys/oracle@demorac as sysdba
...
ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor
分别连接两个节点：
[oracle@bogon 2023_01_28]$ sqlplus sys/oracle@demorac1 as sysdba
...
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.16.0.0.0
SQL>
[oracle@bogon 2023_01_28]$ sqlplus sys/oracle@demorac2 as sysdba
...
ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor
4.尝试relocate监听
看来是因为RAC的实例2连接有问题？
嗯，现在实例2还不存在，那直接把scan配置到节点1机器上试试吧：
[grid@db01rac1 ~]$ srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is running on node db01rac2
[grid@db01rac1 ~]$ srvctl relocate scan_listener -scannumber 1 -node db01rac1
[grid@db01rac1 ~]$ srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is running on node db01rac1
结果依然报错，说明并不是relocate的问题。
其实在relocate之前，就发现scan在节点2时的状态有问题，没有监听到任何服务：
[grid@db01rac2 ~]$ lsnrctl status LISTENER_SCAN1
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 28-JAN-2023 18:54:31
Copyright (c) 1991, 2022, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
STATUS of the LISTENER
------------------------
Alias LISTENER_SCAN1
Version TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date 28-JAN-2023 18:53:51
Uptime 0 days 0 hr. 0 min. 40 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/19.3.0/grid/network/admin/listener.ora
Listener Log File /u01/app/grid/diag/tnslsnr/db01rac2/listener_scan1/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER_SCAN1)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.1.15)(PORT=1521)))
The listener supports no services
The command completed successfully
5.继续排查发现是参数问题
为什么LISTENER_SCAN1监听不到任何服务呢？尝试使用手工alter system register;也不行。
与scan有关的数据库配置就是那个remote参数了，难道设置有问题，oracle用户登陆到数据中查看确认：
SQL> show parameter remote_listener
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
remote_listener string
为什么会是空呢？实际是因为该环境搭建ADG，主库是单实例，参数中没有设置remote_listener参数，备库是RAC，虽然配置了其他RAC独有参数，但漏掉了这个参数。
知道原因后，解决很简单，直接根据当前环境在备库配置正确的 remote_listener 参数值：
alter system set remote_listener='db01rac-scan:1521';
再次查看LISTENER_SCAN1监听状态，已经正常有服务注册了：
[grid@db01rac1 admin]$ lsnrctl status LISTENER_SCAN1
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 28-JAN-2023 19:26:13
Copyright (c) 1991, 2022, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
STATUS of the LISTENER
------------------------
Alias LISTENER_SCAN1
Version TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date 28-JAN-2023 19:15:24
Uptime 0 days 0 hr. 10 min. 49 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/19.3.0/grid/network/admin/listener.ora
Listener Log File /u01/app/grid/diag/tnslsnr/db01rac1/listener_scan1/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER_SCAN1)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.1.15)(PORT=1521)))
Services Summary...
Service "demorac" has 1 instance(s).
Instance "jydb1", status READY, has 1 handler(s) for this service...
The command completed successfully
此时再次测试连接，已恢复正常，ADG链路的报错信息也已经随之解决。
[oracle@bogon 2023_01_28]$ sqlplus sys/oracle@demorac as sysdba
...
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.16.0.0.0
SQL>
6.总结和延伸
本次问题定位后发现很简单，只是因为备库的一个参数设置导致：
# primary 查看配置链路的错误信息：
SQL> select error from v$archive_dest where dest_id = 2;
ERROR
-----------------------------------------------------------------
ORA-12514: TNS:listener does not currently know of service
requested in connect descriptor
# standby 修正参数设置：
alter system set remote_listener='db01rac-scan:1521';
延伸：其实很多ADG同步问题，日志中都会抛出各类错误，除了按照错误排查之外，还有一些经验性的思路，可以在troubleshooting过程中选择尝试，下面给出示例，希望能对大家有所帮助。
1）ADG配置链路defer后再enable：
SQL> alter system set log_archive_dest_state_2=defer;
SQL> alter system set log_archive_dest_state_2=enable;
2）密码文件同步：
[oracle@bogon dbs]$ scp orapwdemo 192.168.1.11:/u01/app/oracle/product/19.3.0/db_1/dbs/orapwjydb1
[oracle@bogon dbs]$ scp orapwdemo 192.168.1.12:/u01/app/oracle/product/19.3.0/db_1/dbs/orapwjydb2
3）重启MRP进程：
RECOVER MANAGED STANDBY DATABASE CANCEL;
RECOVER MANAGED STANDBY DATABASE DISCONNECT;
注意：有时在备库open read only状态下无法启动MRP的情况，可以选择到mount状态下尝试，遇到过很多情况下都有效。
4）尝试重建SRLs：
遇到过个别情况，实时同步有问题是因为SRLs有问题，按照你的环境要求重建即可：
#recreate：drop and create SRLs：
SQL> recover managed standby database cancel;
alter database drop standby logfile group 14;
alter database drop standby logfile group 13;
alter database drop standby logfile group 12;
alter database drop standby logfile group 11;
#确认asm磁盘组中清理，注意千万核对清楚，别误删除其他的：
ASMCMD> rm standby_group_*
ASMCMD> pwd
+datadg/DEMORAC
#新建SRLs：
SQL> select * from v$standby_log;
alter database add standby logfile thread 1 group 11 '+DATADG' size 209715200;
alter database add standby logfile thread 1 group 12 '+DATADG' size 209715200;
alter database add standby logfile thread 1 group 13 '+DATADG' size 209715200;
alter database add standby logfile thread 1 group 14 '+DATADG' size 209715200;
SQL> recover managed standby database disconnect;
5）检查基本参数配置：
很多时候，环境有可能被人修改过，要检查基本参数，确认和你的环境要求匹配：
set linesize 500
col value for a70
col name for a50
select name, value
from v$parameter
where name in ('db_name','db_unique_name','log_archive_config', 'log_archive_dest_1','log_archive_dest_2',
'log_archive_dest_state_1','log_archive_dest_state_2', 'remote_login_passwordfile',
'log_archive_format','log_archive_max_processes','fal_server','db_file_name_convert',
'log_file_name_convert', 'standby_file_management');
6）了解主要进程：
遇到过给生产库配置ADG，但无论如何折腾备库也无法实现实时同步，最终发现是主库有异常，重启后就自动解决了。
但很多情况申请重启主库很难，其实可以先申请尝试重启相关进程，比如主库的arc，tt 等进程。
这些进程被杀掉通常不会导致主库crash，而是会重新启动新的进程。