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Reinstate old Primary Database after Failover


  • Introduction: Reinstating an old primary database after a failover involves transforming the old primary which may have been disabled or fallen out of sync, into a working standby database again. This process, often performed using Flashback Database or managed through DGMGRL, enables it to realign with the new primary without requiring a full database rebuild. In this article, we will Reinstate old primary database after the failover.

  • Methods to reinstate:
    1. Using Flashback Database.
    2. Using Data Guard Broker (DGMGRL).

  • Prerequisites:
    • Flashback Database must be enabled on the old primary.
    • Flashback logs must be available covering the failover point.
    • Standby redo log should exist.
    • Old Primary must not be opened in R/W after failover.
    • DG broker should be configured (for DGMGRL method).

  • Environment:
    • Source Database
    Hostname oradbdc.oraeasy.com
    SID oradbdc
    Database Version 19c (19.28)

    Target Database
    Hostname oradbdr.oraeasy.com
    SID oradbdr
    Database Version 19c (19.28)


  • Summary of activities: We will do reinstate activity with below two methods.

  • Now let's proceed to Reinstate the old Primary step by step:

Using Flashback Database.


1. First verify the precheck at Primary & Standby database. 

Primary.

SQL> def
DEFINE _DATE           = "02-APR-2026" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "oradbdc" (CHAR)
DEFINE _USER           = "SYS" (CHAR)
DEFINE _PRIVILEGE      = "AS SYSDBA" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1928000000" (CHAR)
DEFINE _EDITOR         = "vi" (CHAR)
DEFINE _O_VERSION      = "Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.28.0.0.0" (CHAR)
DEFINE _O_RELEASE      = "1928000000" (CHAR)
SQL>
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role,flashback_on from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    FLASHBACK_ON
--------- ------------------------------ -------------------- ---------------- ------------------
ORADB     oradbdc                        READ WRITE           PRIMARY          YES

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 ORPDB                          READ WRITE NO
SQL>
SQL> col MEMBER for a80
SQL> SELECT group#, type, member FROM v$logfile ORDER BY group#;

    GROUP# TYPE    MEMBER
---------- ------- ------------------------------------------------------------
         1 ONLINE  /u01/app/oracle/oradata/oradbdc/redo01.log
         2 ONLINE  /u01/app/oracle/oradata/oradbdc/redo02.log
         3 ONLINE  /u01/app/oracle/oradata/oradbdc/redo03.log
         4 STANDBY /u01/app/oracle/oradata/oradbdc/standby_redo01.log
         5 STANDBY /u01/app/oracle/oradata/oradbdc/standby_redo02.log
         6 STANDBY /u01/app/oracle/oradata/oradbdc/standby_redo03.log
         7 STANDBY /u01/app/oracle/oradata/oradbdc/standby_redo04.log

7 rows selected.

SQL> set lines 200 pages 300
SQL> alter session set nls_date_format= 'DD-MON-YYYY HH24:MI:SS';

Session altered.

SQL> select d.db_unique_name,d.database_role, a.thread#, b.last_seq, a.applied_seq, a.last_app_timestamp, b.last_seq - a.applied_seq ARC_DIFF
FROM
(select thread#, MASQL> X(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,
(select db_unique_name,database_role from v$database) d where a.thread#=b.thread#;

DB_UNIQUE_NAME                 DATABASE_ROLE       THREAD#   LAST_SEQ APPLIED_SEQ LAST_APP_TIMESTAMP     ARC_DIFF
------------------------------ ---------------- ---------- ---------- ----------- -------------------- ----------
oradbdc                        PRIMARY                   1         47          47 02-APR-2026 21:05:57          0


7 rows selected.

Standby.

SQL> def
DEFINE _DATE           = "02-APR-2026" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "oradbdr" (CHAR)
DEFINE _USER           = "SYS" (CHAR)
DEFINE _PRIVILEGE      = "AS SYSDBA" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1928000000" (CHAR)
DEFINE _EDITOR         = "vi" (CHAR)
DEFINE _O_VERSION      = "Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.28.0.0.0" (CHAR)
DEFINE _O_RELEASE      = "1928000000" (CHAR)
SQL>
SQL> /

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    FLASHBACK_ON
--------- ------------------------------ -------------------- ---------------- ------------------
ORADB     oradbdr                        MOUNTED              PHYSICAL STANDBY YES

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       MOUNTED
         3 ORPDB                          MOUNTED
         
         
SQL> col MEMBER for a80
SQL> SELECT group#, type, member FROM v$logfile ORDER BY group#;

    GROUP# TYPE    MEMBER
---------- ------- ----------------------------------------------------------
         1 ONLINE  /u01/app/oracle/oradata/oradbdr/redo01.log
         2 ONLINE  /u01/app/oracle/oradata/oradbdr/redo02.log
         3 ONLINE  /u01/app/oracle/oradata/oradbdr/redo03.log
         4 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo01.log
         5 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo02.log
         6 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo03.log
         7 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo04.log

7 rows selected

SQL> set lines 200 pages 300
SQL> alter session set nls_date_format= 'DD-MON-YYYY HH24:MI:SS';

Session altered.

SQL> select d.db_unique_name,d.database_role, a.thread#, b.last_seq, a.applied_seq, b.last_seq - a.applied_seq ARC_DIFF, a.last_app_timestamp,
round((sysdate - a.last_app_timestamp)*24*60,2) Gap_in_Mins, round((sysdate - a.last_app_timestamp)*24*60*60,2) Gap_in_Seconds
FROM
(select thread#, MAX(sequence#) applied_seq, MAX(next_time) last_app_timestamp from gv$archived_log where REGISTRAR='RFS' and applied='YES' group by thread#) a,
(select thread#, MAX(sequence#) last_seq from gv$archived_log group by thread#) b,
(select db_unique_name,database_role from v$database) d where a.thread#=b.thread#;

DB_UNIQUE_NAME                 DATABASE_ROLE       THREAD#   LAST_SEQ APPLIED_SEQ   ARC_DIFF LAST_APP_TIMESTAMP   GAP_IN_MINS GAP_IN_SECONDS
------------------------------ ---------------- ---------- ---------- ----------- ---------- -------------------- ----------- --------------
oradbdr                        PHYSICAL STANDBY          1         47          47          0 02-APR-2026 21:05:57        7.83            470
2. Now assume that Primary is not available and let's do the failover. 
 
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     oradbdr                        MOUNTED              PHYSICAL STANDBY

SQL> select d.db_unique_name,d.database_role, a.thread#, b.last_seq, a.applied_seq, b.last_seq - a.applied_seq ARC_DIFF, a.last_app_timestamp,
round((sysdate - a.last_app_timestamp)*24*60,2) Gap_in_Mins, round((sysdate - a.last_app_timestamp)*24*60*60,2) Gap_in_Seconds
FROM
(select thread#, MAX(sequence#) applied_seq, MAX(next_time) last_app_timestamp from gv$archived_log where REGISTRAR='RFS' and applied='YES' group by thread#) a,
(select thread#, MAX(sequence#) last_seq from gv$archived_log group by thread#) b,
(select db_unique_name,database_role from v$database) d where a.thread#=b.thread#;

DB_UNIQUE_NAME                 DATABASE_ROLE       THREAD#   LAST_SEQ APPLIED_SEQ   ARC_DIFF LAST_APP_TIMESTAMP   GAP_IN_MINS GAP_IN_SECONDS
------------------------------ ---------------- ---------- ---------- ----------- ---------- -------------------- ----------- --------------
oradbdr                        PHYSICAL STANDBY          1         47          47          0 02-APR-2026 21:05:57       32.75           1965

SQL> select process,status,thread#,sequence#,block# from v$managed_standby where process like '%MRP%';

PROCESS   STATUS          THREAD#  SEQUENCE#     BLOCK#
--------- ------------ ---------- ---------- ----------
MRP0      APPLYING_LOG          1         48        983

SQL> alter database recover managed standby database cancel;

Database altered.

SQL> alter database recover managed standby database finish;

Database altered.

SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     oradbdr                        MOUNTED              PHYSICAL STANDBY

SQL> alter database activate standby database;

Database altered.

SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     oradbdr                        MOUNTED              PRIMARY

SQL> shut immediate
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area 1962930480 bytes
Fixed Size                  9179440 bytes
Variable Size            1157627904 bytes
Database Buffers          788529152 bytes
Redo Buffers                7593984 bytes
Database mounted.
Database opened.
SQL>
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     oradbdr                        READ WRITE           PRIMARY

SQL>
3. Now let's do the Reinstate activity.
 
On current Primary, check standby_became_primary_scn.

SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     oradbdr                        READ WRITE           PRIMARY

SQL> SELECT to_char(standby_became_primary_scn) FROM v$database;

TO_CHAR(STANDBY_BECAME_PRIMARY_SCN)
----------------------------------------
2687193

On old Primary, Start the listener and database in mount mode.

[oracle@oradbdc ~]$ lsnrctl start

LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 02-APR-2026 22:00:42

Copyright (c) 1991, 2025, Oracle.  All rights reserved.

Starting /u01/app/oracle/product/19c/dbhome_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 19.0.0.0.0 - Production
System parameter file is /u01/app/oracle/product/19c/dbhome_1/network/admin/listener.ora
Log messages written to /u01/app/oracle/diag/tnslsnr/oradbdc/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oradbdc.oraeasy.com)(PORT=1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oradbdc.oraeasy.com)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                02-APR-2026 22:00:42
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/app/oracle/product/19c/dbhome_1/network/admin/listener.ora
Listener Log File         /u01/app/oracle/diag/tnslsnr/oradbdc/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oradbdc.oraeasy.com)(PORT=1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
The listener supports no services
The command completed successfully
[oracle@oradbdc ~]$
[oracle@oradbdc ~]$ sqlplus / as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Thu Apr 2 21:48:52 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2025, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> def
DEFINE _DATE           = "02-APR-26" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "oradbdc" (CHAR)
DEFINE _USER           = "SYS" (CHAR)
DEFINE _PRIVILEGE      = "AS SYSDBA" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1928000000" (CHAR)
DEFINE _EDITOR         = "vi" (CHAR)
DEFINE _O_VERSION      = "" (CHAR)
DEFINE _O_RELEASE      = "" (CHAR)

SQL> startup mount
ORACLE instance started.

Total System Global Area 1962930480 bytes
Fixed Size                  9179440 bytes
Variable Size            1157627904 bytes
Database Buffers          788529152 bytes
Redo Buffers                7593984 bytes
Database mounted.

SQL> set lines 333
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role,flashback_on from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    FLASHBACK_ON
--------- ------------------------------ -------------------- ---------------- ------------------
ORADB     oradbdc                        MOUNTED              PRIMARY          YES

Now run FLASHBACK DATABASE TO SCN to reinstate the Primary.

SQL> FLASHBACK DATABASE TO SCN 2687193;    ==> SCN fetched on current Primary

Flashback complete.

SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY;

Database altered.

SQL> shut immediate
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
SQL>
SQL> startup mount
ORACLE instance started.

Total System Global Area 1962930480 bytes
Fixed Size                  9179440 bytes
Variable Size            1157627904 bytes
Database Buffers          788529152 bytes
Redo Buffers                7593984 bytes
Database mounted.
SQL>

Start the MRP process.

SQL> alter database recover managed standby database disconnect from session;

Database altered.

SQL> select name,DB_UNIQUE_NAME,open_mode, database_role,flashback_on from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    FLASHBACK_ON
--------- ------------------------------ -------------------- ---------------- ------------------
ORADB     oradbdc                        MOUNTED              PHYSICAL STANDBY YES
4. Now do some log switches and check the sync. 
  
At Primary.

SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     oradbdr                        READ WRITE           PRIMARY

SQL> alter system switch logfile;

System altered.

SQL> /

System altered.

SQL> /

System altered.

SQL>

SQL> SELECT MAX(SEQUENCE#) FROM V$ARCHIVED_LOG WHERE DEST_ID = 1 AND ARCHIVED = 'YES' 
     AND RESETLOGS_ID = (SELECT RESETLOGS_ID FROM V$DATABASE_INCARNATION WHERE STATUS = 'CURRENT');

MAX(SEQUENCE#)
--------------
            11
            
At Standby.
            
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    
--------- ------------------------------ -------------------- ---------------- 
ORADB     oradbdc                        MOUNTED              PHYSICAL STANDBY 

SQL> SELECT MAX(SEQUENCE#) FROM V$ARCHIVED_LOG WHERE APPLIED = 'YES'
     AND RESETLOGS_ID = (SELECT RESETLOGS_ID FROM V$DATABASE_INCARNATION WHERE STATUS = 'CURRENT'); 

MAX(SEQUENCE#)
--------------
            11

SQL> select process,status,thread#,sequence#,block# from v$managed_standby where process like '%MRP%';

PROCESS   STATUS          THREAD#  SEQUENCE#     BLOCK#
--------- ------------ ---------- ---------- ----------
MRP0      APPLYING_LOG          1         12        903

Using Data Guard Broker (DGMGRL).


1. First verify the precheck at Primary & Standby database. 

Primary.

SQL> def
DEFINE _DATE           = "07-APR-26" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "oradbdc" (CHAR)
DEFINE _USER           = "SYS" (CHAR)
DEFINE _PRIVILEGE      = "AS SYSDBA" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1928000000" (CHAR)
DEFINE _EDITOR         = "vi" (CHAR)
DEFINE _O_VERSION      = "Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.28.0.0.0" (CHAR)
DEFINE _O_RELEASE      = "1928000000" (CHAR)
SQL>
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role,flashback_on from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    FLASHBACK_ON
--------- ------------------------------ -------------------- ---------------- ------------------
ORADB     ORADBDC                        READ WRITE           PRIMARY          YES

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 ORPDB                          READ WRITE NO
SQL> col MEMBER for a80
SQL> SELECT group#, type, member FROM v$logfile ORDER BY group#;

     GROUP# TYPE    MEMBER
---------- ------- --------------------------------------------------------------------------------
         1 ONLINE  /u01/app/oracle/oradata/ORADB/redo01.log
         2 ONLINE  /u01/app/oracle/oradata/ORADB/redo02.log
         3 ONLINE  /u01/app/oracle/oradata/ORADB/redo03.log
         4 STANDBY /u01/app/oracle/oradata/ORADB/standby_redo01.log
         5 STANDBY /u01/app/oracle/oradata/ORADB/standby_redo02.log
         6 STANDBY /u01/app/oracle/oradata/ORADB/standby_redo03.log
         7 STANDBY /u01/app/oracle/oradata/ORADB/standby_redo04.log
         
7 rows selected.

SQL> set lines 200 pages 300
SQL> alter session set nls_date_format= 'DD-MON-YYYY HH24:MI:SS';

Session altered.

SQL> select d.db_unique_name,d.database_role, a.thread#, b.last_seq, a.applied_seq, a.last_app_timestamp, b.last_seq - a.applied_seq ARC_DIFF
FROM
(select thread#, MASQL> X(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,
(select db_unique_name,database_role from v$database) d where a.thread#=b.thread#;

DB_UNIQUE_NAME   DATABASE_ROLE       THREAD#   LAST_SEQ APPLIED_SEQ LAST_APP_TIMESTAMP     ARC_DIFF
---------------- ---------------- ---------- ---------- ----------- -------------------- ----------
ORADBDC          PRIMARY                   1         45          45 07-APR-2026 21:55:11          0

7 rows selected.

[oracle@oradbdc ~]$ dgmgrl /
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Tue Apr 7 22:09:19 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected to "ORADBDC"
Connected as SYSDG.
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdc - Primary database
    oradbdr - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 16 seconds ago)

DGMGRL>
DGMGRL> show database oradbdc;

Database - oradbdc

  Role:               PRIMARY
  Intended State:     TRANSPORT-ON
  Instance(s):
    oradbdc

Database Status:
SUCCESS

DGMGRL>

Standby.

SQL> def
DEFINE _DATE           = "07-APR-2026" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "oradbdr" (CHAR)
DEFINE _USER           = "SYS" (CHAR)
DEFINE _PRIVILEGE      = "AS SYSDBA" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1928000000" (CHAR)
DEFINE _EDITOR         = "vi" (CHAR)
DEFINE _O_VERSION      = "Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.28.0.0.0" (CHAR)
DEFINE _O_RELEASE      = "1928000000" (CHAR)
SQL>
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role,flashback_on from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    FLASHBACK_ON
--------- ------------------------------ -------------------- ---------------- ------------------
ORADB     oradbdr                        MOUNTED              PHYSICAL STANDBY YES

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       MOUNTED
         3 ORPDB                          MOUNTED
SQL>
SQL> col MEMBER for a80
SQL> SELECT group#, type, member FROM v$logfile ORDER BY group#;

    GROUP# TYPE    MEMBER
---------- ------- --------------------------------------------------------------------------------
         1 ONLINE  /u01/app/oracle/oradata/oradbdr/redo01.log
         2 ONLINE  /u01/app/oracle/oradata/oradbdr/redo02.log
         3 ONLINE  /u01/app/oracle/oradata/oradbdr/redo03.log
         4 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo01.log
         5 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo02.log
         6 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo03.log
         7 STANDBY /u01/app/oracle/oradata/oradbdr/standby_redo04.log

7 rows selected.

SQL> set lines 200 pages 300
SQL> alter session set nls_date_format= 'DD-MON-YYYY HH24:MI:SS';

Session altered.

SQL> select d.db_unique_name,d.database_role, a.thread#, b.last_seq, a.applied_seq, b.last_seq - a.applied_seq ARC_DIFF, a.last_app_timestamp,
round((sysdate - a.last_app_timestamp)*24*60,2) Gap_in_Mins, round((sysdate - a.last_app_timestamp)*24*60*60,2) Gap_in_Seconds
FROM
(select thread#, MAX(sequence#) applied_seq, MAX(next_time) last_app_timestamp from gv$archived_log where REGISTRAR='RFS' and applied='YES' group by thread#) a,
(select thread#, MAX(sequence#) last_seq from gv$archived_log group by thread#) b,
(select db_unique_name,database_role from v$database) d where a.thread#=b.thread#;

DB_UNIQUE_NAME   DATABASE_ROLE       THREAD#   LAST_SEQ APPLIED_SEQ   ARC_DIFF LAST_APP_TIMESTAMP   GAP_IN_MINS GAP_IN_SECONDS
---------------  ---------------- ---------- ---------- ----------- ---------- -------------------- ----------- --------------
oradbdr          PHYSICAL STANDBY          1         45          45          0 07-APR-2026 21:55:11        9.93            596


[oracle@oradbdr ~]$ dgmgrl /
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Tue Apr 7 22:10:12 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected to "oradbdr"
Connected as SYSDG.
DGMGRL>
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdc - Primary database
    oradbdr - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 59 seconds ago)

DGMGRL>
DGMGRL> show database oradbdr

Database - oradbdr

  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      0 seconds (computed 0 seconds ago)
  Apply Lag:          0 seconds (computed 0 seconds ago)
  Average Apply Rate: 6.00 KByte/s
  Real Time Query:    OFF
  Instance(s):
    oradbdr

Database Status:
SUCCESS

DGMGRL>
2. Now assume that Primary is not available and let's do the failover using DGMGRL. 
 
[oracle@oradbdr ~]$ dgmgrl /
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Tue Apr 7 22:18:10 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected to "oradbdr"
Connected as SYSDG.
DGMGRL>
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdc - Primary database
    Error: ORA-12541: TNS:no listener

    oradbdr - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
ERROR   (status updated 0 seconds ago)

DGMGRL>
DGMGRL> show database oradbdc

Database - oradbdc

  Role:               PRIMARY
  Intended State:     TRANSPORT-ON
  Instance(s):
    oradbdc

Database Status:
DGM-17016: failed to retrieve status for database "oradbdc"
ORA-12541: TNS:no listener
ORA-16625: cannot reach member "oradbdc"

DGMGRL> show database oradbdr

Database - oradbdr

  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      0 seconds (computed 293 seconds ago)
  Apply Lag:          0 seconds (computed 293 seconds ago)
  Average Apply Rate: 1.00 KByte/s
  Real Time Query:    OFF
  Instance(s):
    oradbdr

  Database Warning(s):
    ORA-16857: member disconnected from redo source for longer than specified threshold

Database Status:
WARNING

DGMGRL>
DGMGRL> failover to oradbdr;
Performing failover NOW, please wait...
Failover succeeded, new primary is "oradbdr"
DGMGRL>
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdr - Primary database
    oradbdc - Physical standby database (disabled)
      ORA-16661: the standby database needs to be reinstated

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 13 seconds ago)

DGMGRL>
3. Now let's do the Reinstate activity using DGMGRL.
 
On old Primary, Start the listener and database in mount mode.

[oracle@oradbdc ~]$ lsnrctl start
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 07-APR-2026 22:21:40

Copyright (c) 1991, 2025, Oracle.  All rights reserved.

Starting /u01/app/oracle/product/19c/dbhome_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 19.0.0.0.0 - Production
System parameter file is /u01/app/oracle/product/19c/dbhome_1/network/admin/listener.ora
Log messages written to /u01/app/oracle/diag/tnslsnr/oradbdc/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oradbdc.oraeasy.com)(PORT=1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oradbdc.oraeasy.com)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                07-APR-2026 22:21:40
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/app/oracle/product/19c/dbhome_1/network/admin/listener.ora
Listener Log File         /u01/app/oracle/diag/tnslsnr/oradbdc/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oradbdc.oraeasy.com)(PORT=1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
The listener supports no services
The command completed successfully
[oracle@oradbdc ~]$
[oracle@oradbdc ~]$ sqlplus / as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Tue Apr 7 22:21:43 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2025, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup mount
ORACLE instance started.

Total System Global Area 1962930480 bytes
Fixed Size                  9179440 bytes
Variable Size            1157627904 bytes
Database Buffers          788529152 bytes
Redo Buffers                7593984 bytes
Database mounted.
SQL>
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     ORADBDC                        MOUNTED              PRIMARY

SQL>
Now reinstate the old Primary using DGMGRL on current Primary.

[oracle@oradbdr ~]$ dgmgrl /
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Tue Apr 7 22:23:36 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected to "ORADBDR"
Connected as SYSDG.
DGMGRL>
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdr - Primary database
    oradbdc - Physical standby database (disabled)
      ORA-16661: the standby database needs to be reinstated

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 16 seconds ago)

DGMGRL>
DGMGRL> reinstate database oradbdc;
Reinstating database "oradbdc", please wait...
Reinstatement of database "oradbdc" succeeded
DGMGRL>
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdr - Primary database
    oradbdc - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 51 seconds ago)

DGMGRL>

Now check the new standby (old Primary).

SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     ORADBDC                        MOUNTED              PHYSICAL STANDBY
4. Now do some log switches and check the sync. 
  
At Primary.

SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE
--------- ------------------------------ -------------------- ----------------
ORADB     oradbdr                        READ WRITE           PRIMARY

SQL> alter system switch logfile;

System altered.

SQL> /

System altered.

SQL> /

System altered.


SQL> SELECT MAX(SEQUENCE#) FROM V$ARCHIVED_LOG WHERE DEST_ID = 1 AND ARCHIVED = 'YES' 
     AND RESETLOGS_ID = (SELECT RESETLOGS_ID FROM V$DATABASE_INCARNATION WHERE STATUS = 'CURRENT');

MAX(SEQUENCE#)
--------------
            3
            
            
[oracle@oradbdr ~]$ dgmgrl /
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Wed Apr 7 22:27:13 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected to "oradbdr"
Connected as SYSDG.
DGMGRL>
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdr - Primary database
    oradbdc - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 20 seconds ago)

DGMGRL> show database oradbdr

Database - oradbdr

  Role:               PRIMARY
  Intended State:     TRANSPORT-ON
  Instance(s):
    oradbdr

Database Status:
SUCCESS

DGMGRL>

            
At Standby.
            
SQL> select name,DB_UNIQUE_NAME,open_mode, database_role from v$database;

NAME      DB_UNIQUE_NAME                 OPEN_MODE            DATABASE_ROLE    
--------- ------------------------------ -------------------- ---------------- 
ORADB     oradbdc                        MOUNTED              PHYSICAL STANDBY 

SQL> SELECT MAX(SEQUENCE#) FROM V$ARCHIVED_LOG WHERE APPLIED = 'YES'
     AND RESETLOGS_ID = (SELECT RESETLOGS_ID FROM V$DATABASE_INCARNATION WHERE STATUS = 'CURRENT'); 

MAX(SEQUENCE#)
--------------
            3

SQL> select process,status,thread#,sequence#,block# from v$managed_standby where process like '%MRP%';

PROCESS   STATUS          THREAD#  SEQUENCE#     BLOCK#
--------- ------------ ---------- ---------- ----------
MRP0      APPLYING_LOG          1          4      11568

SQL>

[oracle@oradbdc ~]$ dgmgrl /
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Wed Apr 7 22:27:32 2026
Version 19.28.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected to "ORADBDC"
Connected as SYSDG.
DGMGRL>
DGMGRL> show configuration

Configuration - oradbdg

  Protection Mode: MaxPerformance
  Members:
  oradbdr - Primary database
    oradbdc - Physical standby database

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 36 seconds ago)

DGMGRL>
DGMGRL> show database oradbdc

Database - oradbdc

  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      0 seconds (computed 0 seconds ago)
  Apply Lag:          0 seconds (computed 0 seconds ago)
  Average Apply Rate: 18.00 KByte/s
  Real Time Query:    OFF
  Instance(s):
    oradbdc

Database Status:
SUCCESS

DGMGRL>

After Reinstate activity you can do switchover activity as per need. Follow below link.

Switchover to Standby (Manual)
Switchover to Standby (DGMGRL)



Thank you for reading!

I hope this content has been helpful to you. Your feedback and suggestions are always welcome — feel free to leave a comment or reach out with any queries.

Abhishek Shrivastava

📧 Email: oraeasyy@gmail.com
🌐 Website: www.oraeasy.com

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Location: Noida, Uttar Pradesh, India

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