Resizing Redo Logs in a DataGuard Environment

Primary Database: DCPROC

Standby database: DRPROC

Primary Database Server: OPDB1

Standby Database Server: OPDB2

Database version: 11.2.0.2

I have my physical standby database in sync with the primary database with the logs being applied in the form of real time apply. As you might be aware, for the “Real Time Apply” implementation, we need to make sure that we have created the Standby Redo Logs on the standby database with the size same as that of the Online Redo logs. The Standby Redo Logs also needs to be created on the primary database, but this is not mandatory. The Standby Redo Logs would not be used on the Primary database until there is a switchover operation performed and the primary database starts behaving as a standby database. Here is a snippet of the size of the redo logs (Online and Standby Redo logs) on the primary and standby database

Primary Database:

[oracle@dev ~]$ sqlplus sys/oracle@DCPROC as sysdba

SQL*Plus: Release 11.2.0.2.0 Production on Sat Sep 29 16:32:37 2012

Copyright (c) 1982, 2010, Oracle. All rights reserved.

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production

With the Partitioning, Automatic Storage Management, OLAP, DataMining

and Real Application Testing options

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

STATUS INSTANCE_NAME DATABASE_ROLE

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

OPEN   DCPROC        PRIMARY

SQL> select group#,sum(bytes/1024/1024)"Size in MB" from v$log group by group#;

GROUP#     Size in MB

-------    ----------

1          50

2          50

3          50

SQL> select group#,sum(bytes/1024/1024)"Size in MB" from v$standby_log group by group#;

GROUP#   Size in MB

-------  ----------

 6       50

 4       50

 5       50

 7       50

Standby Database:

[oracle@uat ~]$ sqlplus sys/oracle@DRPROC as sysdba

SQL*Plus: Release 11.2.0.2.0 Production on Sat Sep 29 16:47:11 2012

Copyright (c) 1982, 2010, Oracle. All rights reserved.

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production

With the Partitioning, Automatic Storage Management, OLAP, DataMining

and Real Application Testing options

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

STATUS  INSTANCE_NAME  DATABASE_ROLE

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

MOUNTED DRPROC         PHYSICAL STANDBY

SQL> select group#, sum(bytes/1024/1024)"Size in MB" from v$loggroup by group#;

GROUP# Size in MB

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

 1     50

 2     50

 3     50

SQL> select group#,sum(bytes/1024/1024)"Size in MB" from v$standby_log group by group#;

GROUP# Size in MB

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

 4     50

 5     50

 6     50

 7     50

Check if the parameter standby_file_management is set to AUTO or MANUAL on standby database. If it is not set to MANUAL, then set it.

SQL> show parameter standby_file_management

NAME                    TYPE    VALUE

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

standby_file_management string  AUTO

SQL>

SQL>

SQL> alter system set standby_file_management=manual;

System altered.

SQL> show parameter standby_file_management

NAME                     TYPE    VALUE

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

standby_file_management  string  MANUAL

On the primary database, check the status of the Online Redo Logs and resize them by dropping the INACTIVE redo logs and re-creating them with the new size.

Primary:

SQL> select group#,status from v$log;

GROUP# STATUS

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

1      INACTIVE

2      INACTIVE

3      CURRENT

Here you can see that Online Redo Log groups 1 and 2 are INACTIVE. Hence we can drop them and re-create with the new size.

SQL> alter database drop logfile group 1;

Database altered.

SQL> alter database add logfile group 1 size 100M;

Database altered.

SQL> select group#,status from v$log;

GROUP# STATUS

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

1      UNUSED

2      INACTIVE

3      CURRENT

SQL> alter database drop logfile group 2;

Database altered.

SQL> alter database add logfile group 2 size 100M;

Database altered.

SQL> select group#,status from v$log;

GROUP# STATUS

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

1      UNUSED

2      UNUSED

3      CURRENT

Now that Online Redo Log Groups 1 and 2 are resized and the status of Group 3 is CURRENT, switch logfiles manually until Group 3 becomes INACTIVE

After a couple of log switches, we can check the Status of Group 3

SQL> select group#,status from v$log;

GROUP# STATUS

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

1      ACTIVE

2      CURRENT

3      INACTIVE

Now that Group 3 is INACTIVE, we can drop it and re-create it with the new size.

SQL> alter database drop logfile group 3;

Database altered.

SQL> alter database add logfile group 3 size 100M;

Database altered.

Now, we have resized all the Online Redo Logs on the Primary Database from 50M to 100M.

SQL> select group#,sum(bytes/1024/1024)"size in MB" from v$log group by group#;

GROUP# size in MB

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

1      100

2      100

3      100

Moving on to the Standby Redo Logs on the Primary Database:

SQL> select group#,sum(bytes/1024/1024)"size in MB" from v$standby_log group by group#;

GROUP# size in MB

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

6      50

4      50

5      50

7      50

SQL> select group#,status from v$standby_log;

GROUP# STATUS

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

4      UNASSIGNED

5      UNASSIGNED

6      UNASSIGNED

7      UNASSIGNED

The status of the Standby Redo Logs (SRL) on the Primary database would be UNASSIGNED as they would be used only when the primary database starts behaving as a Standby (Switchover)

We can easily drop the UNASSIGNED SRLs and re-create them with the new size.

SQL> alter database drop standby logfile group 4;

Database altered.

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

Database altered.

Repeat this for the remaining SRLs on the primary database and we can see below that all the SRL on the Primary database have been resized.

SQL> select group#,sum(bytes/1024/1024)"size in MB" from v$standby_log group by group#;

GROUP# size in MB

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

6      100

4      100

5      100

7      100

Moving on to the standby database:

Standby:

SQL> select group#,status from v$log;

GROUP# STATUS

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

1      CURRENT

3      CLEARING

2      CLEARING

Lets try to drop Online Redo Log Group 2 as Group 1 is CURRENT status and it cannot be

dropped.

SQL> alter database drop logfile group 2;

alter database drop logfile group 2

*

ERROR at line 1:

ORA-01156: recovery or flashback in progress may need access to files

Here above, we faced ORA-01156 error, which is self-explainatory. The recovery (MRP process) on the standby database is active and it needs to be cancelled before we drop any Redo log groups.

SQL> alter database recover managed standby database cancel;

Database altered.

Since the status of Group 2 is still clearing, lets clear it manually before dropping the group.

SQL> alter database clear logfile group 2;

Database altered.

SQL> alter database drop logfile group 2;

Database altered.

SQL> alter database add logfile group 2 size 100M;

Database altered.

SQL> select group#,status from v$log;

GROUP# STATUS

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

1      CURRENT

3      CLEARING

2      UNUSED

The same is the case with Group 3 whose status is CLEARING. We’ll clear it manually, drop it and create with the new size.

SQL> alter database clear logfile group 3;

Database altered.

SQL> alter database drop logfile group 3;

Database altered.

SQL> alter database add logfile group 3 size 100M;

Database altered.

To drop online redo log group 1 that is in status CURRENT, generate an archive on the primary database by switching logfile, and then clear the CURRENT online redo log group on the standby database, drop it and re-create it with the required size as done for groups 2 and 3 earlier.

SQL> select group#,sum(bytes/1024/1024)"size in MB" from v$log group by group#;

GROUP# size in MB

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

1      100

2      100

3      100

Resizing Standby Redo Logs on standby database:

SQL> select group#,sum(bytes/1024/1024)"size in MB" from v$standby_log group by group#;

GROUP# size in MB

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

4      50

5      50

6      50

7      50

SQL> select group#,status from v$standby_log;

GROUP# STATUS

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

4      ACTIVE

5      UNASSIGNED

6      UNASSIGNED

7      UNASSIGNED

Clear the SRL group whose status is ACTIVE as done earlier, drop the group and re-create them with the size same as that of the Online Redo Logs.

For the SRL groups whose status is UNASSIGNED, just drop the group and recreate them with the size same as that of the Online Redo Logs.

SQL> select group#,sum(bytes/1024/1024)"size in MB" from v$log group by group#;

GROUP# size in MB

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

1      100

2      100

3      100

SQL> select group#,sum(bytes/1024/1024)"size in MB" from v$standby_log group by group#;

GROUP# size in MB

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

4      100

5      100

6      100

7      100

Once all the Standby Redo Logs and Online Redo Logs have been resize on both Primary and standby database, set the STANDBY_FILE_MANAGEMENT to AUTO on the standby database and start the recovery (MRP) on standby database.

SQL> alter system set standby_file_management=auto;

System altered.

SQL> alter database recover managed standby database disconnectfrom session using current logfile;

Database altered.

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

PROCESS STATUS         SEQUENCE#

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

ARCH    CONNECTED      0

ARCH    CLOSING        66

ARCH    CONNECTED      0

ARCH    CLOSING        63

RFS     IDLE           0

RFS     IDLE           0

MRP0    WAIT_FOR_LOG   71

RFS     IDLE           71

RFS     IDLE           0

9 rows selected.

Primary:

SQL> select max(sequence#) from v$archived_log;

MAX(SEQUENCE#)

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

70

Standby:

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

MAX(SEQUENCE#)

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

70