Setting Up a Standby Database
An existing database can be configured to have a standby database. The first
step is to install the Oracle software on the standby server. The database
already exists on the primary server. The primary database will need some
configuration with standby logs and parameters. Connections to the secondary
database can be set up, and then using RMAN, the initial copy of the
database can be set up on the standby server.
On the primary database, the following needs to be done:
SQLPLUS> alter database force logging;
Database altered.
## Create the standby log files. They need to be the
## same size or larger than the primary database
SQLPLUS> alter database add standby logfile
'/u01/oracle/db01/stby01.log' size 50M;
Database altered.
SQLPLUS> alter database add standby logfile
'/u01/oracle/db01/stby02.log' size 50M;
Database altered.

## Continue creating the log files. One more log group
## than on the primary is recommended
## Parameters
SQLPLUS> show parameter db_name
NAME TYPE VALUE

db_name string DB01
## Name stays the same
SQLPLUS> show parameter db_unique_name
NAME TYPE VALUE

db_unique_name string DB01

## Standby and Primary will need unique names
## Names do not change even if roles switch
SQLPLUS> alter system set
LOG_ARCHIVE_CONFIG='DG_CONFIG=(db01,dbstby01)'
System altered.
SQLPLUS> alter system set log_archive_dest_2=
'service=dbstby01 async valid_for=(online_logfile,
primary_role) db_unique_name=dbstby01';
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System altered.
## The standby database server should already have the
## software and the needed directories for the database
## Create a parameter file for the standby with just the DB_NAME
> cat initdbstby01.ora
DB_NAME=dbstby01
> export ORACLE_SID=dbstby01
SQLPLUS> startup nomount pfile=$ORACLE_HOME/dbs/initdbstby01.ora
ORACLE instance started.

SQLPLUS> exit
## To primary database run RMAN to copy database
RMAN> connect target
connected to target database: DB01 (DBID=1382128337)
RMAN> connect auxiliary sysdbstby01
connected to auxiliary database: DBSTBY01 (not mounted)
RMAN> run {
allocate channel disk1 type disk;
allocate auxiliary channel disk2 type disk;
duplicate target database for standby from active database

spfile parameter_value_convert 'db01','dbstby01'
set db_unique_name='dbstby01'
set db_file_name_convert='/db01/','/dbstby01/'
set control_files='/u01/oracle/oradata/dbstby01.ctl'
set fal_client='dbstby01'
set fal_server='db01'
set standby_file_management='AUTO'
set log_archive_config='dg_config=(db01,dbstby01)'
set log_archive_dest_1='service=db01 ASYNC valid_for=
(ONLINE_LOGFILE,PRIMARY_ROLE) db_unique_name=db01';
}

## Can test the standby by switching the log file on the primary
> export ORACLE_SID=DB01
SQLPLUS> alter system switch logfile;
System altered.
In summary, the basic steps are as follows:
1. Install the software on the standby server.
2. Configure the parameters on the primary server.
3. Make the connections by updating tnsnames.ora and listener.
4. Use RMAN to copy the database.
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SQL Server has a manual process for the management of failover for
log shipping. The Oracle Data Guard failover can be configured to occur
automatically. You can use the Data Guard broker and management tools
to set up the automatic failover and manage the standby servers. The Data
Guard broker needs to be running on both the primary and standby server.
A listener entry for the Data Guard broker on the primary and standby
servers will help with failover and avoiding TNS errors.

## Parameter for starting the broker
SQLPLUS> alter system set DG_BROKER_START=TRUE scope=both;
System altered.
## Example listener entry
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = db01_dgmgrl)
(ORACLE_HOME = /u01/oracle/11.2.0/db_1)
(SID_NAME = db01)
)

)
Using the Data Guard broker is similar to starting SQL*Plus from the
command line. Enter dgmgrl to start the utility and then issue commands.
## Create a broker configuration
> dgmgrl
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production
Copyright (c) 2000, 2009, Oracle. All rights reserved.
Welcome to DGMGRL, type "help" for information.
DGMGRL> create configuration 'DG_DB01'
AS PRIMARY DATABASE is 'db01'
CONNECT IDENTIFIER is 'db01';
Configuration "DG_DB01" created with primary database "db01"
DGMGRL> add database 'dbstby01'
AS CONNECT IDENTIFIER is 'dbstby01';
Database "dbstby01" added.
DGMGRL> enable configuration
Enabled.
DGMGRL> show configuration
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Configuration
Name: DG_DB01
Enabled: YES
Protection Mode: MaxAvailability
Databases:
db01 – Primary database
dbstby01 – Physical standby database
Fast-Start Failover: DISABLED
Current status for "DG_DB01': SUCCESS
Other utility commands can be used to do a switchover, which changes
the roles of the servers between primary and standby, or failover, which will
fail the primary over to the standby database.
The default configuration for Fast-Start Failover is disabled.
When it is enabled, it can use triggering events to implement the failover
to the standby server. Events include connection loss, instance crash, a
shutdown abort on the primary, and different database health checks such
as loss of a datafile. With these events, you can set thresholds to have more
control over when the failover occurs. This lets you avoid situations where a
small hiccup in the connection or a busy server that doesn’t allow a quick
check will cause the system to failover.
The Data Guard configurations can be modified to automate the failover
for certain thresholds. If there is more than one standby database, the
FastStartFailoverTarget property should be set so that the primary
and standby database reference each other.
DGMGRL> edit database DB01 set property FastStartFailoverTarget =
'dbstby01';
DGMGRL> edit database DBSTBY01 set property
FastStartFailoverTarget = 'db01';
DGMGRL> edit configuration set property

FastStartFailoverThreshold = '180';
NOTE
With automatic failover, the DBA can be
assured of continuing service without having
to log in. However, the DBA may need to
be concerned about unnecessary failovers.
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Maximum Availability Architecture includes a combination of these
solutions, as shown in Figure 10-5. The Oracle RAC database can be a
primary and a standby server. When the Maximum Protection option is
chosen for the Data Guard configuration, having RAC set up on the standby
database will reduce the risk for the logs to be applied. Figure 10-5 shows
the architecture of the Oracle RAC database with the Data Guard standby
database.
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Interconnect
RAC production database
primary site
Interconnect
RAC standby database
secondary site
Oracle Data Guard
Dedicated network
FIGURE 10-5.
Oracle Maximum Availability Architecture
ASM in an RAC Environment
We have discussed how it is useful to have the ASM instance available for
the disks of the database, but have not yet looked into the details about how

to manage the instance. In the Oracle RAC environment, there needs to be
an ASM instance for every node in the cluster, but one ASM instance can
support multiple instances on that node.
Managing ASM Disk Groups
The ASM disk groups serve as containers for consolidating databases and
file systems to be able to use the storage more efficiently and even share
between databases. The ASM Configuration Assistant (ASMCA) helps you
create and manage disk groups. As shown in Figure 10-6, new disks can be
added to the disk group here, and attributes of the disk group can be edited.
Other ASMCA options allow you to manage the volumes and file system in
a clustered environment.
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FIGURE 10-6.
Using ASMCA
ASMLib is the support library for ASM. It is used for initialize the disk for
usage with ASM. The Linux package for the ASMLib needs to be installed
for usage.
>rpm -Uvh oracleasm-2.6.18-8.el5-2.0.4-1.el5.i686.rpm \
oracleasm-support-2.0.4-1.el5.i386.rpm \
oracleasmlib-2.0.3-1.el5.i386.rpm
## Configure ASMLib
>/etc/init.d/oracleasm configure
Configuring the Oracle ASM library driver.

## Create disks
>/etc/init.d/oracleasm createdisk ORADATA01 /dev/sda1
Marking disk "/dev/sda1" as an ASM disk:
## To see the disks that were created
>/etc/init.d/oracleasm listdisks

ORADATA01
ORADATA02
ORADATA03
ORADATA04
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ASM Configuration Parameters
The ASM instance is really a process and a bit of memory. Some
parameters go into the spfile for configuration of this instance. These
parameters provide the details about the type of instance and where
the disks are located for creating the disk groups.
■
INSTANCE_TYPE Set to ASM (default is RDBMS)
■
ASM_DISKGROUPS Lists the disk groups that should be
mounted
■
ASM_DISKSTRING A value that indicates where to discover
the disks that are available to add to a disk group
■ ASM_POWER_LIMIT Maximum power for rebalancing
operation, a value between 1 and 11 (higher number for faster
rebalancing)
The information stored in the ASM instance is the metadata about the
disks, disk groups, names, and directories. The Oracle database creates
the data in the files when the disk groups are allocated to a database. The
ASMCMD command-line utility can help you manage the files. It provides a
quick way to find out information about what the ASM instance is managing
and where the database files are located. You can take backups, make
copies, and move files. ASMCMD commands are similar to file commands
in a Linux environment. Here are some examples of using ASMCMD:

>asmcmd
ASMCMD> ls –l
State Type Rebal Name
MOUNTED NORMAL N DG_DATA01/
MOUNTED NORMAL N DG_DATA02/
ASMCMD> cd DG_DATA01
ASMCMD> ls –l
Type Redund Striped Time Sys Name
Y ASM/
Y DADEV/
Y DSDEV/
Y SQLTEST/
ASMCMD> cd DADEV
ASMCMD> ls –l
Type Redund Striped Time Sys Name
Y DATAFILE/
Y PARAMETERFILE/
Y TEMPFILE/
N spfileDADEV.ora =>
+DG_DATA01/DADEV/PARAMETERFILE/spfile.269.714035663
## Search for the spfile
ASMCMD> find / spfile*
+DG_DATA01/DADEV/PARAMETERFILE/spfile.269.714035663
+DG_DATA01/DADEV/spfileDADEV.ora
## Check SPACE
ASMCMD> du
Used_MB Mirror_used_MB
23798 47605
## Back up a disk group
ASMCMD> md_backup /bkup/dg1_backup –G 'DG_DATA01'

## The –G parameter is optional; if none chosen, it will
## back up all of the disk groups
## See all connected instances
ASMCMD> lsct
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ASMCMD> lsct
DB_Name Status Compatible_version Instance_Name Disk_Group
+ASM CONNECTED 11.2.0.1.0 +ASM DG_DATA01
DADEV CONNECTED 11.2.0.1.0 DADEV DG_DATA02
DBDEV CONNECTED 11.2.0.1.0 DBDEV DG_DATA02
SQLTEST CONNECTED 11.2.0.1.0 SQLTEST DG_DATA01
These simple commands demonstrate the following:
■
Find out how much space is available on one of the disk groups
■
Find out which instances are connected to which disk groups
■
Find a file
■
Execute a backup of one disk group
With ASM, even though everything is laid out in the directories of the
disk groups, creating tablespaces is very simple. You just use a CREATE
TABLE statement with a disk group and a size.
>export ORACLE_SID=DADEV
>sqlplus
SQLPLUS> create tablespace USER_DATA
datafile '+DG_DATA01' size 2048M;
Tablespace created.
Then you have disk space available for users to start filling up with their

tables, objects, and whatever data they need to store.
As you have come to expect, OEM also offers a way to manage the ASM
disk groups and files. Figure 10-7 shows the OEM display of the disk groups
of the ASM instance. In OEM, the ASM instance is available from any of the
database instances that are using the ASM instance. You can mount the disk
groups through this OEM view.
You can see information about the disks, including the status, the type of
redundancy that the disk is configured for, and the space that is allocated
and used. You can also do some health checks and rebalance the disks.
Selecting one of the disk groups will drill down into a view of the files on
the disks, as shown in Figure 10-8. If you find it difficult to work with the file
names with all of those numbers, you can create an alias or rename files.
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FIGURE 10-7.
OEM view of ASM disk groups
FIGURE 10-8.
OEM view of files in a disk group