d17316 gc20 l06_dataprot_logtrans

6Copyright © 2006, Oracle. All rights reserved.

Configuring Data Protection Modesand Redo Transport Services

Copyright © 2006, Oracle. All rights reserved.6 - 2

Objectives

After completing this lesson, you should be able to do the following:

• Describe the data protection modes

• Change the data protection mode of your configuration

• Modify redo transport services to serve your needs


Data Protection Modes and Redo Transport Modes

• A data protection mode requires a specific redo transport mode.

• A redo transport mode alone does not define a data protection mode.


Defining the Redo Transport Mode

Use the attributes of LOG_ARCHIVE_DEST_n:

• ARCH and LGWR– Specify that either the archiver process or the log writer

process is responsible for transmitting redo to the standby destination

– ARCH is the default.

• SYNC and ASYNC (LGWR only)– Specify that network I/O operations are to be performed

synchronously or asynchronously when using LGWR– SYNC is the default.

• AFFIRM and NOAFFIRM– Ensure that redo has been successfully written to disk on

the standby destination– NOAFFIRM is the default.


Setting the Redo Transport Mode

Click Edit to access the Edit Standby Database Properties

page.


Setting the Redo Transport Mode

Select the mode from the Log Transport Mode

list.


Data Protection Modes

• Three data protection modes:– Maximum protection– Maximum availability– Maximum performance

• Help to balance data availability and system performance


Maximum Protection

• Enables zero data loss• Redo data must be written to both the local online redo

log and the standby redo log on at least one standby database.

• Primary database shuts down if a fault prevents it from writing its redo stream to at least one remote standby redo log.

• Configuration requirements:– Standby redo log files on at least one standby database– SYNC, LGWR, and AFFIRM attributes

for at least one standby database


Maximum Availability

• Enables zero data loss• Provides the highest possible level of data protection

without compromising the availability of the primary database

• Redo data must be written to both the local online redo log and the standby redo log on at least one standby database.

• Primary database does not shut down if a fault prevents it from writing its redo stream.

• Configuration requirements:– Standby redo log files on at least one standby database– SYNC, LGWR, and AFFIRM attributes

for at least one standby database


Maximum Performance

• Default level of data protection

• Provides the highest possible level of data protection without affecting the performance of the primary database

• Transactions can commit as soon as the redo data is written to the local online redo log.

• Redo stream is written asynchronously with respect to the commitment of the transactions that create the redo data.


Setting the Data Protection Mode

Click the Protection Mode link.


Setting the Data Protection Mode


Setting the Data Protection Mode by Using the CLI

1. Configure standby redo logs.

2. Set the LogXptMode property (if necessary).

3. Set the data protection mode.

DGMGRL> EDIT DATABASE 'site1_edrsr8p1' SET PROPERTY 'LogXptMode'='SYNC';DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MAXAVAILABILITY;


Setting the Protection Mode by Using SQL

• You must set attributes to support the type of protection desired.

• Issue the ALTER DATABASE statement on the primary database:

ALTER DATABASE SET STANDBY TO MAXIMIZE PROTECTION;


Delaying the Application of Redo

Delaying the application of redo helps safeguard against:

• Data corruption

• User errors

Productiondatabase

Standbydatabase

Ora

cle

Net Delayed

application


Using Enterprise Manager to Delay the Application of Redo

Specify the delay in minutes.


Setting LOG_ARCHIVE_DEST_n to Delay the Application of Redo

Use the attributes of LOG_ARCHIVE_DEST_n to control the application of redo:

• DELAY: number of minutes to delay application of redo (default: 30 minutes)


Using Flashback Database Instead of Apply Delay

No delay

4-hour delay

Standby1

Standby2

Standby3

8-hour delay

Standby

Primary database

Primary database


Additional Attributes That Affect Redo Transport Services

• ALTERNATE• DEPENDENCY• MAX_FAILURE• NET_TIMEOUT• REOPEN


Using the ALTERNATE Attribute

• Can specify one alternate destination for the LOG_ARCHIVE_DEST_n parameter

• Allow a failed destination to change destinations– Disk full: switch to new disk– Oracle Net link fails: switch to new network link

• Require REOPEN=0 or MAX_FAILURE• Enabled with LOG_ARCHIVE_DEST_STATE_n

log_archive_dest_3='SERVICE=stby1_path1 REOPEN=0 ALTERNATE=LOG_ARCHIVE_DEST_4'log_archive_dest_4='SERVICE=stby1_path2 REOPEN=0 OPTIONAL'log_archive_dest_state_3=ENABLElog_archive_dest_state_4=ALTERNATE


Using the MAX_FAILURE Attribute

MAX_FAILURE[=count]• Number of times redo transport services attempts to

reestablish communication

• Requires REOPEN• No default count

log_archive_dest_3='SERVICE=o10g1 LGWR MAX_FAILURE=30 REOPEN'


Using the NET_TIMEOUT Attribute

• Enables the LGWR process to avoid a network timeout issue

• Valid with SYNC or ASYNC destinations

• Value supplied is the number of seconds to wait.

• Range of values for NET_TIMEOUT: 15 to 1200

• Default: 180• Use caution in maximum protection mode.

log_archive_dest_2='SERVICE=o10g2 LGWR SYNC NET_TIMEOUT=30'


Using the REOPEN Attribute

• REOPEN[=seconds]– Minimum number of seconds to wait before retrying a

failed destination at log switch– Failures can be network failures, quota exceptions, disk

full, and so on.– Default: 300 seconds (5 minutes)

• REOPEN=0– Failed destinations remain disabled until:

— Manually reenabled— ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_n=ENABLE

issued— Instance restart

– Required when using ALTERNATE destinations with MAX_FAILURE=0 attributes


Optimized Asynchronous Redo Transmission

LGWR

Primary database

transactions

Onlineredologs

ARC0

FAL

RFS

MRP or LSP

Archived redo logs

(MRP only)

Archived redo logs

ARC1ARC2

LNSn

Ora

cle

Net

Reports

Backup

Standbydatabase


Enabling Multiple Connectionsfor Remote Archival of Redo

LOG_ARCHIVE_DEST_3='SERVICE=detroit MAX_CONNECTIONS=5'

The following conditions must be met to enable this feature:

• Remote archiving is performed to disk.

• LOG_ARCHIVE_LOCAL_FIRST must be set to TRUE (default).


Summary

In this lesson, you should have learned how to:

• Describe the data protection modes

• Change the data protection mode of your configuration

• Modify redo transport services to suit your needs

• Delay the application of redo

• Use additional transport services attributes


Practice 6: Overview

This practice covers the following topics:

• Changing the data protection mode

• Delaying the application of redo

d17316 gc20 l06_dataprot_logtrans

Technology

data loss redo data

primarydatabase redo

redo data iswritten

redo stream

transmitting redo

standby redo log files

remote standby redo

data protection modeclick