没有F5 没有域名解析，DG如何实现简单访问

单机的主备库，如果没有集群软件，当主备切换后，客户端连接串往往需要修改，有条件的地方将IP设置为一个域名，例如 hrdb.huawei.com（仅是举例，如有雷同纯属巧合），然后切换DG，网络方面将这个域名指向备库IP(或F5分发到备库IP)，客户端不用改动就可以继续访问数据库了。没有域名解析或F5怎么办？

用一个即将淘汰的技术 services_name，亲测oracle 19.9有效

创建一个服务：
exec dbms_service.create_service(service_name=>'appservice',network_name=>'appservice')

连接串这样设置：
ORCL =
  (DESCRIPTION_LIST =
       (FAILOVER = ON)
       (LOAD_BALANCE = OFF)
       (DESCRIPTION =
         (ADDRESS_LIST =
            (ADDRESS = (PROTOCOL = TCP)(HOST = bjdb)(PORT = 1521))
        )
       (CONNECT_DATA =
            (SERVICE_NAME = appservice)
        )
    )
       (DESCRIPTION =
            (ADDRESS_LIST =
            (ADDRESS = (PROTOCOL = TCP)(HOST = shdb)(PORT = 1521))
          )
         (CONNECT_DATA =
            (SERVICE_NAME = appservice)
         )
       )
  )

主库创建触发器：
CREATE OR REPLACE TRIGGER service_name_trg
  AFTER DB_ROLE_CHANGE ON DATABASE
DECLARE
  role VARCHAR(30);
BEGIN
  SELECT DATABASE_ROLE INTO role FROM V$DATABASE;
  IF role = 'PRIMARY' THEN
    DBMS_SERVICE.START_SERVICE('appservice');
  ELSE
    DBMS_SERVICE.STOP_SERVICE('appservice');
  END IF;
END;
/

重启主库

客户端测试
sqlplus scott/tiger@orcl
select host_name from v$instance; --连接到bjdb  北京
切换到备库
sqlplus scott/tiger@orcl
select host_name from v$instance; --连接到shdb  上海

透明，当然会话会中断，客户端需要能自动重新连接（tomcat连接池基本功能）。

官方推荐的技术 TAC



通过 srvctl 实现配置（开始找不同）

--BASIC SERVICE
srvctl add service -db mydb -service MYSERVICE
–preferred inst1 -available inst2 -pdb mypdb -notification TRUE
-drain_timeout 300 -stopoption IMMEDIATE -role PRIMARY

--TAC
$ srvctl add service -db mydb -service TACSERVICE
-pdb mypdb –preferred inst1 -available inst2
-failover_restore AUTO -commit_outcome TRUE
-failovertype AUTO -replay_init_time 600
-retention 86400 -notification TRUE
-drain_timeout 300 -stopoption IMMEDIATE -role PRIMARY

--AC
$ srvctl add service -db mydb -service ACSERVICE
-pdb mypdb -preferred inst1 -available inst2
-failover_restore LEVEL1 -commit_outcome TRUE
-failovertype TRANSACTION -session_state dynamic
-replay_init_time 600 -retention 86400 -notification TRUE
-drain_timeout 300 -stopoption IMMEDIATE -role PRIMARY

最好是RAC  ->  RAC的ADG，连接串例子
引自：bilibili.com/video/BV1AX4y1u7zm?spm_id_from=333.999.0.0

检查服务状态

set pagesize 60
set lines 120
col Service_name format a30 trunc heading "Service"
break on con_id skip1
col Total_requests format 999,999,9999 heading "Requests"
col Total_calls format 9,999,9999 heading "Calls in requests"
col Total_protected format 9,999,9999 heading "Calls Protected"
col Protected format 999.9 heading "Protected %"
select con_id, service_name, total_requests,
total_calls,total_protected,total_protected*100/NULLIF(total_calls,0) as
Protected
from(
select * from
(select a.con_id, a.service_name, c.name,b.value
FROM gv$session a, gv$sesstat b, gv$statname c
WHERE a.sid = b.sid
AND a.inst_id = b.inst_id
AND b.value != 0
AND b.statistic# = c.statistic#
AND b.inst_id = c.inst_id
AND a.service_name not in ('SYS$USERS','SYS$BACKGROUND'))
pivot(
sum(value)
for name in ('cumulative begin requests' as total_requests, 'cumulative end
requests' as Total_end_requests, 'cumulative user calls in requests' as
Total_calls, 'cumulative user calls protected by Application Continuity' as
total_protected) ))
order by con_id, service_name;

参考：oracle.com/goto/ac