Oracle 19c Data Guard Switchover Procedure – Step-by-Step Guide

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Purpose

This guide describes a step-by-step approach to perform a switchover in an Oracle Data Guard configuration.

Prerequisites

  • Primary and Standby are healthy and synchronized.
  • Both databases are under clusterware control.
  • SYSDBA connectivity is available.
  • Application services are stopped before switchover.

Environment Details
Primary Database PRD_CDB
Standby Database STBY_CDB
Primary Server PRD_NODE1
Standby Server STBY_NODE1

Switchover Procedure (With Actual Output)

1. Remove DelayMins (if configured)

DGMGRL> connect sys/<password>
DGMGRL> show database PRD_CDB delaymins;
DGMGRL> edit database PRD_CDB set property 'DelayMins'='0';
DGMGRL> show database PRD_CDB delaymins;

Sample Output:

DelayMins = '180'
Property "DelayMins" updated
DelayMins = '0'

2. Shut Down Application Services

Ensure all application connections to PRD_CDB are stopped.

3. Validate Archive Destinations

SELECT DEST_NAME, STATUS, DESTINATION
FROM V$ARCHIVE_DEST
WHERE DESTINATION IS NOT NULL;

4. Check Primary Database Status

DGMGRL> SHOW DATABASE 'PRD_CDB';

Sample Output:

Database - PRD_CDB
  Role:               PRIMARY
  Intended State:     TRANSPORT-ON
  Instance(s):
    prd1
    prd2

Database Status:
SUCCESS

5. Check Standby Database Status

DGMGRL> SHOW DATABASE VERBOSE 'STBY_CDB';

Sample Output:

Database - STBY_CDB
  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Apply Lag:          0 seconds
  Transport Lag:      (unknown)
  Instance(s):
    stby1 (apply instance)
    stby2

Database Status:
SUCCESS

6. Validate Databases for Switchover

DGMGRL> validate database PRD_CDB;
DGMGRL> validate database STBY_CDB;

Sample Output:

Ready for Switchover:  Yes
Flashback Database:    Off
Managed by Clusterware: YES

7. Perform Switchover

DGMGRL> SWITCHOVER TO STBY_CDB;

Sample Output:

Performing switchover NOW, please wait...
Connected to "STBY_CDB" as SYSDBA.
New primary database "STBY_CDB" is opening...
Oracle Clusterware is restarting database "PRD_CDB" ...
Switchover succeeded, new primary is "STBY_CDB"

8. Post-Switchover Verification

DGMGRL> SHOW CONFIGURATION;

Sample Output:

Configuration Status: SUCCESS

Primary:   STBY_CDB
Standby:   PRD_CDB
Frequently Asked Questions:
1. What is a switchover in Oracle Data Guard?
A switchover is a planned role reversal where the primary database
becomes standby and the standby database becomes primary without
data loss.

2.What conditions must be met before performing a
switchover?
     
  • Standbydatabase must be in sync with primary.
  • RedoApply must be running.
  • No archivegap.
  • DG Broker configuration must be valid.
  • Databases should be ready for switchover (DGMGRL VALIDATE).


3. What does the “VALIDATE DATABASE” command check?
It checks:
  • Database sync status
    •  
  • Apply lag and transport lag
    •  
  • Archive gaps
    •  
  • Flashback availability
    •  
  • Clusterware management
    •  
  • Whether databases are ready for role transition
4. What is “Apply Lag” and “Transport Lag”?
     
  • Apply Lag – delay between redo applied on standby vs primary.
    •  
  • Transport Lag – delay in redo shipping.
Zero lag is ideal before switchover
5. What do you do if switchover fails halfway?


6. How do you check if a DB is ready for switchover?
DGMGRL> VALIDATE DATABASE <db_name>;
7. How do you check Data Guard configuration after
switchover?
DGMGRL> SHOW CONFIGURATION;
DGMGRL> SHOW DATABASE <db_name>;
8. What should DBAs check post-switchover?
New primary open read/write
Old primary running as standby
Apply running
Archive log shipping
Services running correctly

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