6 configuring data protection modes and redo transport services

6

Configuring Data Protection Modes
and Redo Transport Services

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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

6-2

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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.

6-3

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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.
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Setting the Redo Transport Mode

Click Edit to access the
Edit Standby Database Properties
page.
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Setting the Redo Transport Mode

Select the mode from
the Log Transport Mode
list.

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Data Protection Modes

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

• Help to balance data availability and system
performance

6-8

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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

6-9

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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

6 - 10

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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.

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Setting the Data Protection Mode

Click the Protection Mode

link.

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Setting the Data Protection Mode

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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;

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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;

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Delaying the Application of Redo

Production
database
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Oracle Net

Delaying the application of redo helps safeguard against:
• Data corruption
• User errors

Delayed
application

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Standby

database


Using Enterprise Manager to Delay
the Application of Redo

Specify the delay in
minutes.

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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)

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Using Flashback Database
Instead of Apply Delay
Standby1
No delay

Primary
database

Standby2
4-hour delay

Standby3
8-hour delay

Primary
database

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Standby

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Additional Attributes That Affect
Redo Transport Services
•
•
•
•
•

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ALTERNATE

DEPENDENCY
MAX_FAILURE
NET_TIMEOUT
REOPEN

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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=ENABLE
log_archive_dest_state_4=ALTERNATE
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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'

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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'

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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
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Optimized Asynchronous Redo Transmission
Primary
database
transactions

MRP or
LSP

Standby
database

(MRP only)
LNSn

RFS

Oracle Net

LGWR

Online
redo
logs
FAL

Backup
Reports

ARC0
ARC1
ARC2
Archived redo
logs
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Archived redo
logs
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Enabling Multiple Connections
for Remote Archival of Redo
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).
LOG_ARCHIVE_DEST_3=
'SERVICE=detroit MAX_CONNECTIONS=5'

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