Switch over and switch back database using DATAGUARD broker

 
Switch over and switch back database using DATAGUARD broker
==========================================
Check the  Database Is Ready for a Role Change
It will checks whether it is ready for switchover.

DGMGRL> VALIDATE DATABASE 'ORCL';

DGMGRL> VALIDATE DATABASE 'ORCL';

  Database Role:    Primary database
  Ready for Switchover:  Yes
  Flashback Database Status:
    orcl:  Off
  Managed by Clusterware:
    orcl:  NO
    Validating static connect identifier for database orcl...
Unable to connect to database using (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=rac8.samik.com)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=ORCL_DGMGRL)(INSTANCE_NAME=ORCL)(SERVER=DEDICATED)(STATIC_SERVICE=TRUE)))
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor
Failed.
    Warning: Ensure primary database's StaticConnectIdentifier property
    is configured properly so that the primary database can be restarted
    by DGMGRL after switchover



---------
Oracle Data Guard Broker and Static Service Registration (Doc ID 1387859.1)
Note: Static "_DGMGRL" entries are no longer needed as of Oracle Database 12.1.0.2 in Oracle Data Guard Broker configurations that are managed by Oracle Restart, RAC On Node or RAC as the Broker will use the clusterware to restart an instance.

Solution:- 
edit database ORCL set property StaticConnectIdentifier='ORCL';

===================
Connect to the Primary Instance : using dgmgrl utility

Before Switchover status (Primary):

SQL> select status,instance_name,database_role from v$database,v$instance;
STATUS       INSTANCE_NAME    DATABASE_ROLE
------------ ---------------- ----------------
OPEN         ORCL             PRIMARY

Before Switchover status (Standby):

SQL> select status,instance_name,database_role from v$database,v$instance;
STATUS       INSTANCE_NAME    DATABASE_ROLE
------------ ---------------- ----------------
MOUNTED      ORCLDG           PHYSICAL STANDBY

-------------Actual Switchover--------------------

[oracle@rac8 ~]$ dgmgrl sys/sys#123@ORCL
DGMGRL for Linux: Release 18.0.0.0.0 - Production on Wed Aug 18 01:26:44 2021
Version 18.3.0.0.0
Copyright (c) 1982, 2018, Oracle and/or its affiliates.  All rights reserved.
Welcome to DGMGRL, type "help" for information.
Connected to "ORCL"
Connected as SYSDBA.
DGMGRL>

DGMGRL>
DGMGRL> switchover to ORCLDG;
Performing switchover NOW, please wait...
Operation requires a connection to database "orcldg"
Connecting ...
Connected to "ORCLDG"
Connected as SYSDBA.
New primary database "orcldg" is opening...
Operation requires start up of instance "ORCL" on database "orcl"
Starting instance "ORCL"...
Unable to connect to database using ORCL
ORA-12505: TNS:listener does not currently know of SID given in connect descriptor
Failed.
Warning: You are no longer connected to ORACLE.
Please complete the following steps to finish switchover:
        start up and mount instance "ORCL" of database "orcl"
DGMGRL>
DGMGRL>
DGMGRL>
DGMGRL> exit

[oracle@rac8 ~]$

[oracle@rac8 ~]$ ps -ef| grep smon
grid      24391      1  0 Aug17 ?        00:00:00 asm_smon_+ASM
oracle    87178  32455  0 02:28 pts/1    00:00:00 grep --color=auto smon
[oracle@rac8 ~]$

-------Check the database status at Standby with become primary now-------

STATUS       INSTANCE_NAME    DATABASE_ROLE
------------ ---------------- ----------------
OPEN         ORCLDG           PRIMARY


[oracle@rac8 ~]$ sqlplus '/as sysdba'
SQL*Plus: Release 18.0.0.0.0 - Production on Wed Aug 18 02:36:03 2021
Version 18.3.0.0.0
Copyright (c) 1982, 2018, Oracle.  All rights reserved.
Connected to an idle instance.

SQL> startup nomount;
ORACLE instance started.
Total System Global Area 1174403152 bytes
Fixed Size                  8656976 bytes
Variable Size             436207616 bytes
Database Buffers          721420288 bytes
Redo Buffers                8118272 bytes
SQL>
SQL>
SQL> alter database mount standby database;
Database altered.

---Primary 07 -- 
SQL> alter system switch logfile;
SQL> alter system switch logfile;
SQL> alter system switch logfile;
SQL> alter system switch logfile;
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            +DATA/orcldg
Oldest online log sequence     353
Next log sequence to archive   355
Current log sequence           355

---Standby 08 --Automatically enable MRP by broker-

SQL> SELECT ARCH.THREAD# "Thread", ARCH.SEQUENCE# "Last Sequence Received", APPL.SEQUENCE# "Last Sequence Applied", (ARCH.SEQUENCE# - APPL.SEQUENCE#) "Difference" FROM (SELECT THREAD# ,SEQUENCE# FROM V$ARCHIVED_LOG  WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$ARCHIVED_LOG GROUP BY THREAD#)) ARCH, (SELECT THREAD# ,SEQUENCE# FROM V$LOG_HISTORY WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$LOG_HISTORY GROUP BY THREAD#)) APPL WHERE ARCH.THREAD# = APPL.THREAD# ORDER BY 1;

    Thread Last Sequence Received Last Sequence Applied Difference
---------- ---------------------- --------------------- ----------
         1                    354                   354          0

[oracle@rac7 ~]$ dgmgrl
DGMGRL for Linux: Release 18.0.0.0.0 - Production on Wed Aug 18 02:41:13 2021
Version 18.3.0.0.0
Copyright (c) 1982, 2018, Oracle and/or its affiliates.  All rights reserved.
Welcome to DGMGRL, type "help" for information.
DGMGRL>
DGMGRL>
DGMGRL> connect sys/sys#123@ORCLDG
Connected to "ORCLDG"
Connected as SYSDBA.
DGMGRL>
DGMGRL>
DGMGRL>
DGMGRL> show configuration;
Configuration - my_dg_config
  Protection Mode: MaxPerformance
  Members:
  orcldg - Primary database
    orcl   - Physical standby database
Fast-Start Failover: DISABLED
Configuration Status:
SUCCESS   (status updated 13 seconds ago)
DGMGRL>

--Run the command newly become Primary---Switchback from rac7 to rac8

DGMGRL>
DGMGRL> switchover to ORCL;
Performing switchover NOW, please wait...
Operation requires a connection to database "orcl"
Connecting ...
Connected to "ORCL"
Connected as SYSDBA.
New primary database "orcl" is opening...
Oracle Clusterware is restarting database "orcldg" ...
Connected to "ORCLDG"
Connected to "ORCLDG"
Switchover succeeded, new primary is "orcl"
DGMGRL>

Note:- We could see that DB was in mount state but when we switchover from rac8 to rac7, DB got down.

[oracle@rac7 ~]$ ps -ef | grep smon
grid      24624      1  0 Aug17 ?        00:00:00 asm_smon_+ASM
oracle    82039      1  0 02:44 ?        00:00:00 ora_smon_ORCLDG
oracle    82462  28479  0 02:46 pts/1    00:00:00 grep --color=auto smon
[oracle@rac7 ~]$
[oracle@rac7 ~]$
[oracle@rac7 ~]$ sqlplus '/as sysdba'
SQL*Plus: Release 18.0.0.0.0 - Production on Wed Aug 18 02:46:16 2021
Version 18.3.0.0.0
Copyright (c) 1982, 2018, Oracle.  All rights reserved.

Connected to:
Oracle Database 18c Enterprise Edition Release 18.0.0.0.0 - Production
Version 18.3.0.0.0

SQL> select status from v$instance;
STATUS
------------
MOUNTED

[oracle@rac8 ~]$ sqlplus '/as sysdba'
SQL*Plus: Release 18.0.0.0.0 - Production on Wed Aug 18 02:48:58 2021
Version 18.3.0.0.0
Copyright (c) 1982, 2018, Oracle.  All rights reserved.

Connected to:
Oracle Database 18c Enterprise Edition Release 18.0.0.0.0 - Production
Version 18.3.0.0.0

SQL> select status,instance_name,database_role from v$database,v$instance;
STATUS       INSTANCE_NAME    DATABASE_ROLE
------------ ---------------- ----------------
OPEN         ORCL             PRIMARY