Changing Protection Mode in a Dataguard Environment

Primary Database :  SRPRIM
Standby Database :  SRPSTB
Database version   :  11gR2

The database is running under Maximum Performance mode.

SQL> select status,instance_name,database_role,protection_mode from v$database,v$instance;

STATUS INSTANCE_NAME DATABASE_ROLE PROTECTION_MODE
------ ------------- ------------- --------------------
OPEN   srprim        PRIMARY       MAXIMUM PERFORMANCE

In order to change the protection mode to either MAXIMUM AVAILABILITY/MAXIMUM PROTECTION, we need to have the standby redo logs configured on
the standby database. Also, the redo shippment parameter (log_archive_dest_2) on the primary database should be configured to use SYNCHRONOUS
(“SYNC”) mode.

Let’s check the number of online redo logs and it’s size on primary database

SQL> select group#,bytes/1024/1024 from v$log;

GROUP# BYTES/1024/1024
------ ------------------
1      100
2      100
3      100

It can be noticed from below that there are no standby redo log groups configured on the primary database.

SQL> select group#,bytes/1024/1024 from v$standby_log;

no rows selected

Add standby redo log groups on the primary database with the same size as that of the online redo log groups.

SQL> alter database add standby logfile group 4 size 100M;

Database altered.

SQL> alter database add standby logfile group 5 size 100M;

Database altered.

SQL> alter database add standby logfile group 6 size 100M;

Database altered.

SQL> alter database add standby logfile group 7 size 100M;

Database altered.

We can now notice that 4 standby redo log groups have been added with the same size as that of the online redo logs.
These standby redo logs will not be used on the primary database and will be used only when a switchover takes place.

SQL> select group#,bytes/1024/1024 from v$standby_log;

GROUP# BYTES/1024/1024
------ ---------------
4      100
5      100
6      100
7      100

SQL> select thread#,max(sequence#) from v$archived_log group bythread#;

THREAD# MAX(SEQUENCE#)
------- --------------
1       311

Standby:

SQL> select thread#,max(sequence#) from v$archived_log where applied='YES' group by thread#;

THREAD# MAX(SEQUENCE#)
------- --------------
1       311

Standby database is in sync with the primary database.

Standby database details:

SQL> select status,instance_name,database_role from v$database,v$Instance;

STATUS  INSTANCE_NAME DATABASE_ROLE
------- ------------- ------------------
MOUNTED srpstb        PHYSICAL STANDBY

On the standby database, there are 3 online redo log groups with the size 100M and there are no standby redo log groups.

SQL> select group#,bytes/1024/1024 from v$log;

GROUP# BYTES/1024/1024
------ ----------------
1      100
3      100
2      100

SQL> select group#,bytes/1024/1024 from v$standby_log;

no rows selected

Let’s add standby redo log groups on the standby database but before that, we need to check if MRP (Managed Recovery Process) is running on
the standby database and if running, then it needs to be cancelled.

SQL> select process,status,sequence# from v$managed_standby;

PROCESS STATUS       SEQUENCE#
------- ------------ ----------
ARCH    CONNECTED    0
ARCH    CONNECTED    0
ARCH    CONNECTED    0
ARCH    CONNECTED    0
RFS     IDLE         0
RFS     IDLE         0
RFS     IDLE         0
MRP0    WAIT_FOR_LOG 312

8 rows selected.

Cancel the MRP process on the standby database:

SQL> alter database recover managed standby database cancel;

Database altered.

Add 4 Standby Redo Log (SRL) groups of size same as online redo log groups (100M) on the standby database:

SQL> alter database add standby logfile group 4 size 100M;

Database altered.

SQL> alter database add standby logfile group 5 size 100M;

Database altered.

SQL> alter database add standby logfile group 6 size 100M;

Database altered.

SQL> alter database add standby logfile group 7 size 100M;

Database altered.

SQL> select group#,bytes/1024/1024 from v$standby_log;

GROUP# BYTES/1024/1024
------ ---------------
4      100
5      100
6      100
7      100

Once the SRLs are added, start the MRP on the standby database

SQL> alter database recover managed standby database disconnectfrom session;

Database altered.

SQL> select process,status,sequence# from v$managed_standby;

PROCESS STATUS       SEQUENCE#
------- -----------  ----------
ARCH    CONNECTED    0
ARCH    CONNECTED    0
ARCH    CONNECTED    0
ARCH    CONNECTED    0
RFS     IDLE         0
RFS     IDLE         0
RFS     IDLE         0
MRP0    WAIT_FOR_LOG 312

8 rows selected.

As said earlier, configure the redo shippment parameter (log_archive_dest_2) on the primary database to use SYNCHRONOUS mode.

Primary database:

SQL> show parameter log_archive_dest_2

NAME               TYPE   VALUE
------------------ ------ -----------------------------------
log_archive_dest_2 string service=srpstb valid_for=(online_logf                          iles,primary_role) db_unique_name=srp                          stb

SQL> alter system set log_archive_dest_2='service=srpstb LGWR AFFIRM SYNC valid_for=(online_logfiles,primary_role) db_unique_name=srpstb';

System altered.

SQL> show parameter dest_2

NAME                        TYPE   VALUE
--------------------------- ------ ----------------------------
db_create_online_log_dest_2 string
log_archive_dest_2          string service=srpstb LGWR AFFIRM                              SYNC valid_for=(online_logfiles,p
                            rimary_role) db_unique_name=srpstb

Shutdown the primary database and mount it.

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

Total System Global Area 208769024 bytes
Fixed Size 2226936 bytes
Variable Size 180356360 bytes
Database Buffers 20971520 bytes
Redo Buffers 5214208 bytes
Database mounted.
SQL>

Now change the protection mode on the primary database according to the requirement using the below command

“alter database set standby database to maximize {AVAILABILITY | PROTECTION| PERFORMANCE}”

Here, I am changing the protection mode from MAXIMUM PERFORMANCE to MAXIMUM AVAILABILITY

SQL> alter database set standby database to maximize availability;

Database altered.

Once the mode is changed, open the primary database and verify the same.

SQL> alter database open;

Database altered.

SQL> select status,instance_name,database_role,protection_mode from v$database,v$instance;

STATUS INSTANCE_NAME DATABASE_ROLE PROTECTION_MODE
------ ------------- ------------- ----------------------
OPEN   srprim        PRIMARY       MAXIMUM AVAILABILITY

Check if the standby database is in sync with the primary database

On primary:

SQL> select thread#,max(sequence#) from v$archived_log group bythread#;

THREAD# MAX(SEQUENCE#)
------- --------------
1       316

Standby:

SQL> select status,instance_name,database_role,protection_mode from v$database,v$instance;

STATUS  INSTANCE_NAME DATABASE_ROLE    PROTECTION_MODE
------- ------------- ---------------- --------------------
MOUNTED srpstb        PHYSICAL STANDBY MAXIMUM AVAILABILITY

SQL> select thread#,max(sequence#) from v$archived_log where applied='YES' group by thread#;

THREAD# MAX(SEQUENCE#)
------- --------------
 1      316

Standby database is in sync with the primary and also the PROTECTION mode has been changed to MAXIMUM AVAILABILITY.

Here we go !!

 

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