Switchover Operation Procedure:
After configuring data guard, databases would be either primary and standby database role, and we can altered these roles without loss of data or without resetting logs called Switchover.
A database can be in one of two mutually exclusive modes (primary or standby). These roles can be altered at runtime without loss of data or resetting of redo logs. This process is known as a Switchover and can be performed using the following statements.
Data guard Configuration Details:-
Step 1:- Check database role and database name
Primary database:-
SQL> select name,open_mode,database_role from v$database; NAME OPEN_MODE DATABASE_ROLE --------- -------------------- ---------------- DBWR READ WRITE PRIMARY
Standby database:-
SQL> select name,open_mode,database_role from v$database; NAME OPEN_MODE DATABASE_ROLE --------- -------------------- ---------------- DBWR MOUNTED PHYSICAL STANDBY
Precheck for Switchover:- (PRIMARY SIDE)
Before performing switchover, kindly verify the state of data guard on both the instances by following SQL queries:
Step 2:-
SQL> ALTER SESSION SET nls_date_format='DD-MON-YYYY HH24:MI:SS'; Session altered.
SQL> SELECT sequence#, first_time, next_time, applied FROM v$archived_log ORDER BY sequence#; SEQUENCE# FIRST_TIME NEXT_TIME APPLIED ---------- -------------------- -------------------- --------- 3 13-MAR-2019 18:59:20 13-MAR-2019 23:55:09 NO 4 13-MAR-2019 23:55:09 14-MAR-2019 20:04:18 NO 5 14-MAR-2019 20:04:18 14-MAR-2019 20:43:17 NO 6 14-MAR-2019 20:43:17 15-MAR-2019 01:35:09 NO 7 15-MAR-2019 01:35:09 15-MAR-2019 22:57:54 NO 8 15-MAR-2019 22:57:54 16-MAR-2019 00:11:18 NO 8 15-MAR-2019 22:57:54 16-MAR-2019 00:11:18 YES 9 16-MAR-2019 00:11:18 16-MAR-2019 00:47:08 NO 9 16-MAR-2019 00:11:18 16-MAR-2019 00:47:08 YES 10 16-MAR-2019 00:47:08 16-MAR-2019 01:54:56 NO 10 16-MAR-2019 00:47:08 16-MAR-2019 01:54:56 YES 11 rows selected.
Step 3:-
SQL> select switchover_status from v$database; SWITCHOVER_STATUS -------------------- TO STANDBY
Note: This command will give you appropriate message about the data guard current status.
After getting confirmation on data guard smooth activity, we can instantiate switchover activity by issuing following sort of commands:
The switchover_status column of v$database can have the following values:
Not Allowed:-Either this is a standby database and the primary database has not been switched first, or this is a primary database and there are no standby databases
Session Active:- Indicates that there are active SQL sessions attached to the primary or standby database that need to be disconnected before the switchover operation is permitted
Switchover Pending:- This is a standby database and the primary database switchover request has been received but not processed.
Switchover Latent:- The switchover was in pending mode, but did not complete and went back to the primary database
To Primary:- This is a standby database, with no active sessions, that is allowed to switch over to a primary database
To Standby:- This is a primary database, with no active sessions, that is allowed to switch over to a standby database
Recovery Needed:- This is a standby database that has not received the switchover request
On Primary database:-
Step 4:
SQL> alter database commit to switchover to standby; Database altered.
Step 5:-
shutdown immediate
startup nomount
alter database mount standby database
[oracle@ram dbs]$ sqlplus / as sysdba SQL*Plus: Release 19.0.0.0.0 - Production on Sat Mar 16 02:20:17 2019 Version 19.2.0.0.0 Copyright (c) 1982, 2018, Oracle. All rights reserved. Connected to an idle instance. SQL> startup nomount ORACLE instance started. Total System Global Area 2415917872 bytes Fixed Size 8899376 bytes Variable Size 654311424 bytes Database Buffers 1744830464 bytes Redo Buffers 7876608 bytes SQL> alter database mount standby database; Database altered. SQL> alter database recover managed standby database disconnect from session; Database altered.
Step 6:-
SQL> select name,open_mode,database_role from v$database; NAME OPEN_MODE DATABASE_ROLE --------- -------------------- ---------------- DBWR READ WRITE PRIMARY
On Standby database:
Step 7:-alter database commit to switchover to primary;
SQL> alter database commit to switchover to primary; Database altered.
Step 8:-
SQL> select name,open_mode,database_role from v$database; NAME OPEN_MODE DATABASE_ROLE --------- -------------------- ---------------- DBWR MOUNTED PRIMARY
Switch over activity have completed successfully, our old primary database has become standby and old standby database has become primary database.
Note:-To test above switchover activity, generate multiple archive logs on primary database and verify those archive logs being transferred on standby database.
After switchover activity,
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