DATAGUARD, PHYSICAL & LOGICAL STANDBY
Question & Answers
o Question 1. What Is Data Guard?
Answer :
Data Guard
provides a comprehensive set of services that create, maintain, manage, and
monitor one or more standby databases to enable production Oracle databases to
survive disasters and data corruptions. Data Guard maintains these standby
databases as copies of the production database. Data Guard can be used with
traditional backup, restoration, and cluster techniques to provide a high level
of data protection and data availability.
o Question 2. What Is Dg Broker?
Answer :
DG Broker “it
is the management and monitoring tool”.
Oracle
dataguard broker is a distributed management framework that automates and
centralizes the creation , maintenance and monitoring of DG configuration.
All management
operations can be performed either through OEM, which uses the broker (or)
broker specified command-line tool interface “DGMGRL”.
o Question 3. What Is The Difference Between
Data Guard And Standby?
Answer :
Data Guard : Dataguard is
mechanism/tool to maintain standby database. The dataguard is set up between
primary and standby instance . Data Guard is only available on Enterprise
Edition.
Standby Database : Physical
standby database provides a physically identical copy of the primary database,
with on disk database structures that are identical to the primary database on
a block-for-block basis. Standby capability is available on Standard Edition.
o Question 4. What Are The Differences Between
Physical/logical Standby Databases? How Would You Decide Which One Is Best
Suited For Your Environment?
Answer :
Physical standby DB: As the name,
it is physically (datafiles, schema, other physical identity) same copy of the
primary database. It synchronized with the primary database with Apply Redo to
the standby DB.
Logical Standby DB: As the name
logical information is the same as the production database, it may be physical
structure can be different.
It
synchronized with primary database though SQL Apply, Redo received from the
primary database into SQL statements and then executing these SQL statements on
the standby DB.
We can open
“physical stand by DB to “read only” and make it available to the applications
users (Only select is allowed during this period). we can not apply redo logs
received from primary database at this time.
We do not see
such issues with logical standby database. We can open the database in normal
mode and make it available to the users. At the same time, we can apply
archived logs received from primary database.
For OLTP large
transaction database it is better to choose logical standby database.
o Question 5. Explain Active Data Guard?
Answer :
11g Active
Data Guard
Oracle Active
Data Guard enables read-only access to a physical standby database for queries,
sorting, reporting, web-based access, etc., while continuously applying changes
received from the production database.
Oracle Active
Data Guard also enables the use of fast incremental backups when offloading
backups to a standby database, and can provide additional benefits of high availability
and disaster protection against planned or unplanned outages at the production
site.
o
Question 6. What Are Differences Between
Physical, Logical, Snapshot Standby And Adg (or) What Are Different Types Of
Standby Databases?
Answer :
Physical standby – in mount
state, MRP will apply archives
ADG – in READ ONLY
state, MRP will apply archives
Logical standby – in READ ONLY
state, LSP will run
Snapshot
standby databases – Physical standby database can be converted to snapshot
standby database, which will be in READ WRITE mode, can do any kind of testing,
then we can convert back snapshot standby database to physical standby database
and start MRP which will apply all pending archives.
o Question 7. How To Find Out Backlog Of
Standby?
Answer :
select
round((sysdate – a.NEXT_TIME)*24*60) as “Backlog”,m.SEQUENCE#-1 “Seq
Applied”,m.process, m.status
from
v$archived_log a, (select process,SEQUENCE#, status from v$managed_standby
where process like ‘%MRP%’)m where a.SEQUENCE#=(m.SEQUENCE#-1);
o Question 8. If You Didn’t Have Access To The
Standby Database And You Wanted To Find Out What Error Has Occurred In A Data
Guard Configuration, What View Would You Check In The Primary Database To Check
The Error Message?
Answer :
You can check
the v$dataguard_status view.
select message
from v$dataguard_status;
o Question 9. How Can U Recover Standby Which
Far Behind From Primary (or) Without Archive Logs How Can We Make Standby Sync?
Answer :By using RMAN
incremental backup.
o Question 10. What Is Snapshot Standby (or)
How Can We Give A Physical Standby To User In Read Write Mode And Let Him Do
Updates And Revert Back To Standby?
Answer :
Till Oralce
10g, create guaranteed restore point, open in read write, let him do updates,
flashback to restore point, start MRP.
From
Oracle 11g, convert physical standby to snapshot standby, let him do updates,
convert to physical standby, start MRP.
o
Question 11. What Are New Features In 11g
Data Guard?
Answer :
Here is some data guard category and there
enhancement
o Data Protection Advanced Compression Lost-write protection Fast-Start
Failover
o Increase ROI Active Data Guard Snapshot Standby
o High Availability Faster Redo Apply Faster failover & switchover
Automatic Failover using ASYNC
o Manageability Mixed Windows/Linux
o Question 12. What Are The Uses Of Standby
Redo Log Files?
Answer :
A standby redo
log is required for the maximum protection and maximum availability modes and
the LGWR ASYNC transport mode is recommended for all databases. Data Guard can
recover and apply more redo data from a standby redo log than from archived
redo log files alone.
If the
real-time apply feature is enabled, log apply services can apply redo data as
it is received, without waiting for the current standby redo log file to be
archived.
This results
in faster switchover and failover times because the standby redo log files have
been applied already to the standby database by the time the failover or
switchover begins.
o Question 13. What Is Dg_config ?
Answer :
Specify the
DG_CONFIG attribute to identify the DB_UNIQUE_NAME for the primary database and
each standby database in the Data Guard configuration.
The default
value of this parameter enables the primary database to send redo data to
remote destinations and enables standby databases to receive redo data.
o Question 14. What Is Rta (real Time Apply)
Mode Mrp?
Answer :
real-time
apply where before log shipping the LGWR process writes to a standbylog file
simultaneously along with the online redolog file.
This standby
logfile is written to standby log file on standby server. There is no loss of
any committed transaction whatsoever in Real-Time Apply scenario.
•In
Real Time Apply, once a transaction is committed on the Primary, the committed
changes will be available on the Standby in Real Time even without switching
the log at the Primary
MRP – Managed recovery process
– For Data Guard, the background process that applies archived redo log to the
standby database.
o Question 15. What Is The Difference Between
Sync/async, Lgwr/arch, And Affirm/noaffirm ?
Answer :
Specifies
that network I/O is to be done synchronously (SYNC) or asynchronously (ASYNC)
when archival is performed using the log writer process (LGWR).
Specifies
whether redo transport services use archiver processes (ARCn) or the log writer
process (LGWR) to collect transaction redo data and transmit it to standby
destinations. If neither the ARCH or LGWR attributes are specified, the default
is ARCH.
Controls
whether redo transport services use synchronous or asynchronous I/O to write
redo data to disk
AFFIRM—specifies that all disk I/O
to archived redo log files and standby redo log files is performed
synchronously and completes successfully before the log writer process continues.
NOAFFIRM—specifies that all disk I/O
to archived redo log files and standby redo log files is performed
asynchronously; the log writer process on the primary database does not wait
until the disk I/O completes before continuing.
o Question 16. What Is Staticconnectidentifier
Property Used For?
Answer :11gr2 new
database property, StaticConnectIdentifier, which allows the user to specify a
static connect identifier that the DGMGRL client will use to start database
instances.
Question 17. What Is Failover/switchover (or)
What Is The Difference Between Failover And Switchover?
Answer :
Switchover – This is
done when both primary and standby databases are available. It is pre-planned.
Failover – This is
done when the primary database is NO longer available (ie in a Disaster). It is
not pre-planned.
o Question 18. What Are The Background
Processes Involved In Data Guard?
Answer :
MRP, LSP
o Question 19. What Are Different Types Of
Modes In Data Guard And Which Is Default?
Answer :
Maximum performance:
This
is the default protection mode.
It
provides the highest level of data protection that is possible without
affecting the performance of a primary database.
This
is accomplished by allowing transactions to commit as soon as all redo data
generated by those transactions has been written to the online log.
Maximum protection:
This
protection mode ensures that no data loss will occur if the primary database
fails.
To
provide this level of protection, the redo data needed to recover a transaction
must be written to both the online redo log and to at least one standby
database before the transaction commits.
To
ensure that data loss cannot occur, the primary database will shut down, rather
than continue processing transactions.
Maximum availability:
This
protection mode provides the highest level of data protection that is possible
without compromising the availability of a primary database.
Transactions
do not commit until all redo data needed to recover those transactions has been
written to the online redo log and to at least one standby database.
o Question 20. How Many Standby Databases We
Can Create (in 10g/11g)?
Answer :
Till Oracle
10g, 9 standby databases are supported.
From Oracle
11g R2, we can create 30 standby databases..
o Question 21. What Are The Parameters We’ve To
Set In Primary/standby For Data Guard ?
Answer :
DB_UNIQUE_NAME
LOG_ARCHIVE_CONFIG
LOG_ARCHIVE_MAX_PROCESSES
DB_CREATE_FILE_DEST
DB_FILE_NAME_CONVERT
LOG_FILE_NAME_CONVERT
LOG_ARCHIVE_DEST_n
LOGARCHIVE_DEST_STATE_n
FAL_SERVER
FAL_CLIENT
STANDBY_FILE_MANAGEMENT
o Question 22. What Is The Use Of Fal_server
& Fal_client, Is It Mandatory To Set These ?
Answer :
FAL_SERVER
specifies
the FAL (fetch archive log) server for a standby database. The value is an
Oracle Net service name, which is assumed to be configured properly on the
standby database system to point to the desired FAL server.
FAL_CLIENT
specifies
the FAL (fetch archive log) client name that is used by the FAL service,
configured through the
FAL_SERVER
initialization parameter, to refer to the FAL client.
The value is
an Oracle Net service name, which is assumed to be configured properly on the
FAL server system to point to the FAL client (standby database).
o Question 23. What Is A Snapshot Standby
Database?
Answer :
11g
Snapshot Standby Database
Oracle
11g introduces the Snapshot Standby database which essentially is an updateable
standby database which has been created from a physical standby database.
We can
convert a physical standby database to a snapshot standby database, do some
kind of testing on a database which is a read write copy of the current primary
or production database and then finally revert it to it’s earlier state
as a physical standby database.
While
the snapshot standby database is open in read-write mode, redo is being
received from the primary database, but is not applied.
After
converting it back to a physical standby database, it is resynchronized with
the primary by applying the accumalated redo data which was earlier shipped
from the primary database but not applied.
Using a
snapshot standby, we are able to do real time application testing using near
real time production data. Very often we are required to do production clones
for the purpose of testing. But using snapshot standby databases we can meet
the same requirement sparing the effort,time,resources and disk space.
o Question 24. Snapshot Standby Database
(updatable Snapshot For Testing)?
Answer :
A
snapshot standby database is a fully updatable standby database that is created
by converting a physical standby database into a snapshot standby database.
Like a
physical or logical standby database, a snapshot standby database receives and
archives redo data from a primary database. Unlike a physical or logical
standby database, a snapshot standby database does not apply the redo data that
it receives. The redo data received by a snapshot standby database is not
applied until the snapshot standby is converted back into a physical standby
database, after first discarding any local updates made to the snapshot standby
database.
o Question 25. Data Guard Architecture?
Answer :
Data Guard Configurations:
A Data
Guard configuration consists of one production database and one or more standby
databases. The databases in a Data Guard configuration are connected by Oracle
Net and may be dispersed geographically. There are no restrictions on where the
databases are located, provided they can communicate with each other.
Dataguard
Architecture
The Oracle 9i Data Guard architecture incorporates the
following items:
o Primary Database – A production database that is used to create standby
databases. The archive logs from the primary database are transfered and
applied to standby databases. Each standby can only be associated with a single
primary database, but a single primary database can be associated with multiple
standby databases.
o Standby Database – A replica of the primary database.
o Log Transport Services – Control the automatic transfer of archive redo log
files from the primary database to one or more standby destinations.
o Network Configuration – The primary database is connected to one or more
standby databases using Oracle Net.
o Log Apply Services – Apply the archived redo logs to the standby database.
The Managed Recovery Process (MRP) actually does
the work of maintaining and applying the archived redo logs.
o Role Management Services – Control the changing of database roles from
primary to standby. The services include switchover, switchback and failover.
o Data Guard Broker – Controls the creation and monitoring of Data Guard. It
comes with a GUI and command line interface.
Primary Database:
A Data Guard
configuration contains one production database, also referred to as the primary
database, that functions in the primary role. This is the database that is
accessed by most of your applications.
Standby Database:
A
standby database is a transactionally consistent copy of the primary database.
Using a backup copy of the primary database, you can create up to nine standby
databases and incorporate them in a Data Guard configuration. Once created,
Data Guard automatically maintains each standby database by transmitting redo
data from the primary database and then applying the redo to the standby database.
The types of standby databases are as follows:
Physical standby database:
Provides
a physically identical copy of the primary database, with on disk database
structures that are identical to the primary database on a block-for-block
basis. The database schema, including indexes, are the same. A physical standby
database is kept synchronized with the primary database, through Redo Apply,
which recovers the redo data received from the primary database and applies the
redo to the physical standby database.
Logical standby database:
Contains
the same logical information as the production database, although the physical
organization and structure of the data can be different. The logical standby
database is kept synchronized with the primary database through SQL Apply,
which transforms the data in the redo received from the primary database into
SQL statements and then executes the SQL statements on the standby database.
o Question 26. What Are The Services Required
On The Primary And Standby Database ?
Answer :
The services required on the primary database are:
o Log Writer Process (LGWR) – Collects redo information and updates the
online redo logs. It can also create local
archived redo logs and transmit online redo to standby databases.
o Archiver Process (ARCn) – One or more archiver processes make copies of
online redo logs either locally or remotely for standby databases.
o Fetch Archive Log (FAL) Server – Services requests for archive redo logs
from FAL clients running on multiple standby databases. Multiple FAL servers
can be run on a primary database, one for each FAL request. .
o The services required on the standby database are:
o Fetch Archive Log (FAL) Client – Pulls archived redo log files from the
primary site. Initiates transfer of archived redo logs when it detects a gap
sequence.
o Remote File Server (RFS) – Receives archived and/or standby redo logs from
the primary database.
o Archiver (ARCn) Processes – Archives the standby redo logs applied by the
managed recovery process (MRP).
o Managed Recovery Process (MRP) – Applies archive redo log information to
the standby database
o Question 27. What Is Rts (redo Transport
Services) In Data Guard?
Answer :
It controls
the automated transfer of redo data from the production database to one or more
archival destinations.
The redo transport services perform the
following tasks:
o Transmit redo data from the primary system to the standby systems in the
configuration.
o Manage the process of resolving any gaps in the archived redo log files due
to a network failure.
o Automatically detect missing or corrupted archived redo log files on a
standby system and automatically retrieve replacement archived redo log files
from the primary database or another standby database.
o Question 28. What Are The Protection Modes In
Dataguard?
Answer :
Data
Guard Protection Modes
This
section describes the Data Guard protection modes.
In
these descriptions, a synchronized standby database is meant to be one that
meets the minimum requirements of the configured data protection mode and that
does not have a redo gap. Redo gaps are discussed in Section 6.3.3.
Maximum Availability
This
protectionmode provides the highest level of data protection that is possible
without compromising the availability of a primary database. Transactions do
not commit until all redo data needed to recover those transactions has been
written to the online redo log and to at least one synchronized standby
database. If the primary database cannot write its redo stream to at least one
synchronized standby database, it operates as if it were in maximum performance
mode to preserve primary database availability until it is again able to write
its redo stream to a synchronized standby database.
This
mode ensures that no data loss will occur if the primary database fails, but
only if a second fault does not prevent a complete set of redo data from being
sent from the primary database to at least one standby database.
Maximum Performance
This
protectionmode provides the highest level of data protection that is possible
without affecting the performance of a primary database. This is accomplished
by allowing transactions to commit as soon as all redo data generated by those
transactions has been written to the online log. Redo data is also written to
one or more standby databases, but this is done asynchronously with respect to
transaction commitment, so primary database performance is unaffected by delays
in writing redo data to the standby database(s).
This
protection mode offers slightly less data protection than maximum availability
mode and has minimal impact on primary database performance.
This
is the default protection mode.
Maximum Protection
This
protection mode ensures that zero data loss occurs if a primary database fails.
To provide this level of protection, the redo data needed to recover a
transaction must be written to both the online redo log and to at least one
synchronized standby database before the transaction commits. To ensure that
data loss cannot occur, the primary database will shut down, rather than
continue processing transactions, if it cannot write its redo stream to at
least one synchronized standby database.
Because
this data protection mode prioritizes data protection over primary database
availability, Oracle recommends that a minimum of two standby databases be used
to protect a primary database that runs in maximum protection mode to prevent a
single standby database failure from causing the primary database to shut down.
o Question 29. How To Delay The Application Of
Logs To A Physical Standby?
Answer :
A
standby database automatically applies redo logs when they arrive from the
primary database. But in some cases, we want to create a time lag between the
archiving of a redo log at the primary site, and the application of the log at
the standby site.
Modify
the LOG_ARCHIVE_DEST_n initialization parameter on the primary database to set
a delay for the standby database.
Example: For 60min Delay:
ALTER
SYSTEM SET LOG_ARCHIVE_DEST_2=’SERVICE=stdby_srvc DELAY=60′;
The
DELAY attribute is expressed in minutes.
The archived
redo logs are still automatically copied from the primary site to the standby
site, but the logs are not immediately applied to the standby database. The
logs are applied when the specified time interval expires.
o Question 30. Steps To Create Physical Standby
Database?
Answer :
o Take a full hot backup of Primary database
o Create standby control file
o Transfer full backup, init.ora, standby control file to standby node.
o Modify init.ora file on standby node.
o Restore database
o Recover Standby database(Alternatively, RMAN DUPLICATE DATABASE FOR STANDBY
DO RECOVERY can be also used)
o Setup FAL_CLIENT and FAL_SERVER parameters on both sides
o Put Standby database in Managed Recover mode
o Question 31. What Are The Data Guard
Parameters In Oracle?
Answer :
Set Primary
Database Initialization Parameters
———————————————-
On the primary
database, you define initialization parameters that control redo transport
services while the database is in the primary role. There are additional
parameters you need to add that control the receipt of the redo data and log
apply services when the primary database is transitioned to the standby role.
DB_NAME=chicago
DB_UNIQUE_NAME=chicago
LOG_ARCHIVE_CONFIG=’DG_CONFIG=(chicago,boston)’
CONTROL_FILES=’/arch1/chicago/control1.ctl’,
‘/arch2/chicago/control2.ctl’
LOG_ARCHIVE_DEST_1=
‘LOCATION=/arch1/chicago/
VALID_FOR=(ALL_LOGFILES,ALL_ROLES)
DB_UNIQUE_NAME=chicago’
LOG_ARCHIVE_DEST_2=
‘SERVICE=boston
LGWR ASYNC
VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)
DB_UNIQUE_NAME=boston’
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_STATE_2=ENABLE
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
LOG_ARCHIVE_FORMAT=%t_%s_%r.arc
LOG_ARCHIVE_MAX_PROCESSES=30
Primary
Database: Standby Role Initialization Parameters
FAL_SERVER=boston
FAL_CLIENT=chicago
DB_FILE_NAME_CONVERT=’boston’,’chicago’
LOG_FILE_NAME_CONVERT=
‘/arch1/boston/’,’/arch1/chicago/’,’/arch2/boston/’,’/arch2/chicago/’
STANDBY_FILE_MANAGEMENT=AUTO
Prepare
an Initialization Parameter File for the Standby Database
—————————————————————–
Create
a text initialization parameter file (PFILE) from the server parameter file
(SPFILE) used by the primary database; a text initialization parameter file can
be copied to the standby location and modified. For example:
CREATE
PFILE=’/tmp/initboston.ora’ FROM SPFILE;
Modifying
Initialization Parameters for a Physical Standby Database.
DB_NAME=chicago
DB_UNIQUE_NAME=boston
LOG_ARCHIVE_CONFIG=’DG_CONFIG=(chicago,boston)’
CONTROL_FILES=’/arch1/boston/control1.ctl’,
‘/arch2/boston/control2.ctl’
DB_FILE_NAME_CONVERT=’chicago’,’boston’
LOG_FILE_NAME_CONVERT=
‘/arch1/chicago/’,’/arch1/boston/’,’/arch2/chicago/’,’/arch2/boston/’
LOG_ARCHIVE_FORMAT=log%t_%s_%r.arc
LOG_ARCHIVE_DEST_1=
‘LOCATION=/arch1/boston/
VALID_FOR=(ALL_LOGFILES,ALL_ROLES)
DB_UNIQUE_NAME=boston’
LOG_ARCHIVE_DEST_2=
‘SERVICE=chicago LGWR ASYNC
VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=chicago’
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_STATE_2=ENABLE
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE
STANDBY_FILE_MANAGEMENT=AUTO
FAL_SERVER=chicago
FAL_CLIENT=boston
o Question 32. What Are The Types Of Oracle
Data Guard?
Answer :
Oracle Data
Guard classified in to two types based on way of creation and method used for
Redo Apply.
They are as follows:
o Physical standby (Redo Apply technology)
o Logical standby (SQL Apply Technology)
o Question 33. What Are The Advantages In Using
Oracle Data Guard?
Answer :
Following are the different benefits in using
Oracle Data Guard feature in your environment:
o High Availability.
o Data Protection.
o Off loading Backup operation to standby database.
o Automatic Gap detection and Resolution in standby database.
o Automatic Role Transition using Data Guard Broker.
o Question 34. What Are The Different Services
Available In Oracle Data Guard?
Answer :
Following are
the different Services available in Oracle Data Guard of Oracle database.
o Redo Transport Services.
o Log Apply Services.
o Role Transitions.
o Question 35. What Are The Different
Protection Modes Available In Oracle Data Guard?
Answer :
Following are
the different protection modes available in Data Guard of Oracle database you
can use any one based on your application requirement.
o Maximum Protection
o Maximum Availability
o Maximum Performance.
o Question 36. How To Check What Protection
Mode Of Primary Database In Your Oracle Data Guard?
Answer :
By using
following query you can check protection mode of primary database in your
Oracle Data Guard setup. SELECT PROTECTION_MODE FROM V$DATABASE;
For Example: SQL>
select protection_mode from v$database;
PROTECTION_MODE
——————————–
MAXIMUM
PERFORMANCE
o Question 37. How To Change Protection Mode In
Oracle Data Guard Setup?
Answer :
By using
following query your can change the protection mode in your primary database
after setting up required value in corresponding LOG_ARCHIVE_DEST_n parameter
in primary database for corresponding standby database. ALTER DATABASE SET
STANDBY DATABASE TO MAXIMUM [PROTECTION|PERFORMANCE|AVAILABILITY];
Example: alter
database set standby database to MAXIMUM PROTECTION;
o Question 38. What Are The Advantages Of Using
Physical Standby Database In Oracle Data Guard?
Answer :
Advantages of using Physical standby database in Oracle
Data Guard are as follows:
o High Availability.
o Load balancing (Backup and Reporting).
o Data Protection.
o Disaster Recovery.
o Question 39. What Is Physical Standby
Database In Oracle Data Guard?
Answer :
Oracle Standby
database are divided into physical standby database or logical standby database
based on standby database creation and redo log apply method. Physical standby
database are created as exact copy i.e block by block copy of primary database.
In physical standby database transactions happen in primary database are
synchronized in standby database by using Redo Apply method by continuously
applying redo data on standby database received from primary database.
Physical
standby database can offload the backup activity and reporting activity from
Primary database. Physical standby database can be opened for read-only
transactions but redo apply won’t happen during that time. But from 11g onwards
using Active Data Guard option (extra purchase) you can simultaneously open the
physical standby database for read-only access and apply redo logs received
from primary database.
o Question 40. What Is Logical Standby Database
In Oracle Data Guard?
Answer :
Oracle Standby
database are divided into physical standby database or logical standby database
based on standby database creation and redo log apply method. Logical standby
database can be created similar to Physical standby database and later you can
alter the structure of logical standby database. Logical standby database uses
SQL Apply method to synchronize logical standby database with primary database.
This SQL apply
technology converts the received redo logs to SQL statements and continuously
apply those SQL statements on logical standby database to make standby database
consistent with primary database. Main advantage of Logical standby database
compare to physical standby database is you can use Logical standby database
for reporting purpose during SQL apply i.e Logical standby database must be
open during SQL apply.
Even though
Logical standby database are opened for read/write mode, tables which are in
synchronize with primary database are available for read-only operations like
reporting, select queries and adding index on those tables and creating
materialized views on those tables. Though Logical standby database has
advantage on Physical standby database it has some restriction on data-types,
types of DDL, types of DML and types of tables.
o Question 41. What Are The Advantages Of
Logical Standby Database In Oracle Data Guard?
Answer :
o Better usage of resource
o Data Protection
o High Availability
o Disaster Recovery
o Question 42. What Is The Usage Of
Db_file_name_convert Parameter In Oracle Data Guard Setup?
Answer :
DB_FILE_NAME_CONVERT
parameter is used in Oracle Data Guard setup that to in standby databases.
DB_FILE_NAME_CONVERT parameter are used to update the location of data files in
standby database. These parameter are used when you are using different
directory structure in standby database compare to primary database data files
location.
o Question 43. What Is The Usage Of
Log_file_name_convert Parameter In Oracle Data Guard Setup?
Answer :
LOG_FILE_NAME_CONVERT
parameter is used in Oracle Data Guard setup that to in standby databases. LOG_FILE_NAME_CONVERT
parameter are used to update the location of redo log files in standby
database. These parameter are used when you are using different directory
structure in standby database compare to primary database redo log file
location.
Step
for Physical Standby
These are the steps to follow:
o Enable forced logging
o Create a password file
o Configure a standby redo log
o Enable archiving
o Set up the primary database initialization parameters
o Configure the listener and tnsnames to support the database on both nodes
o col name format a20
o col thread# format 999
o col sequence# format 999
o col first_change# format 999999
o col next_change# format 999999
SELECT
thread#, sequence# AS “SEQ#”, name, first_change# AS “FIRSTSCN”,
next_change#
AS “NEXTSCN”,archived, deleted,completion_time AS “TIME”
FROM
v$archived_log
V$ log_history
o Question 44. Tell Me About Parameter Which Is
Used For Standby Database?
Answer :
o Log_Archive_Dest_n
o Log_Archive_Dest_State_n
o Log_Archive_Config
o Log_File_Name_Convert
o Standby_File_Managment
o DB_File_Name_Convert
o DB_Unique_Name
o Control_Files
o Fat_Client
o Fat_Server
The
LOG_ARCHIVE_CONFIG parameter enables or disables the sending of redo streams to
the standby sites. The DB_UNIQUE_NAME of the primary database is dg1 and the DB_UNIQUE_NAME
of the standby database is dg2. The primary database is configured to ship redo
log stream to the standby database. In this example, the standby database
service is dg2.
Next,
STANDBY_FILE_MANAGEMENT is set to AUTO so that when Oracle files are added or
dropped from the primary database, these changes are made to the standby
databases automatically. The STANDBY_FILE_MANAGEMENT is only applicable to the
physical standby databases.
Setting the
STANDBY_FILE_MANAGEMENT parameter to AUTO is is recommended when using Oracle
Managed Files (OMF) on the primary database. Next, the primary database must be
running in ARCHIVELOG mode.
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