Changing Protection Mode in DataGuard Environment

Primary Database :  DCPROC

Standby Database :  PRPROC

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   DCPROC        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 DRPROC        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 disconnect from 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=DRPROC valid_for=(online_logfiles,primary_role)

                           db_unique_name=DRPROC

                    

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

System altered.

SQL> show parameter dest_2

NAME                        TYPE   VALUE

--------------------------- ------ --------------------------------------------------

db_create_online_log_dest_2 string

log_archive_dest_2          string service=DRPROC LGWR AFFIRM SYNC valid_for=                                             (online_logfiles,primary_role) db_unique_name=DRPROC   

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   DCPROC        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 DRPROC        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.