AFFIRM and NOAFFIRM
Controls whether a redo transport destination acknowledges received redo data before or after writing it to the standby redo log:
AFFIRM—specifies that a redo transport destination acknowledges received redo data after writing it to the standby redo log.
NOAFFIRM—specifies that a redo transport destination acknowledges received redo data before writing it to the standby redo log.
If neither the AFFIRM nor the NOAFFIRM attribute is specified, the default is AFFIRM when the SYNC attribute is specified and NOAFFIRM when theASYNC attribute is specified.
Specification of the AFFIRM attribute without the SYNC attribute is deprecated and will not be supported in future releases.
The following example shows the AFFIRM attribute for a remote destination.
LOG_ARCHIVE_DEST_3='SERVICE=stby1 SYNC AFFIRM'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
ALTERNATE
Specifies an alternate archiving destination to be used when the original destination fails.
LOG_ARCHIVE_DEST_11 through LOG_ARCHIVE_DEST_31 cannot be specified as an alternate redo transport location.
The ALTERNATE attribute is optional. If an alternate destination is not specified, then redo transport services do not automatically change to another destination if the original destination fails.
You can specify only one alternate destination for each LOG_ARCHIVE_DEST_n parameter, but several enabled destinations can share the same alternate destination.
Ideally, an alternate destination should specify either:
If no enabled destinations reference an alternate destination, the alternate destination is implied to be deferred, because there is no automatic method of enabling the alternate destination. However, you can enable (or defer) alternate destinations at runtime using ALTER SYSTEM.
Any destination can be designated as an alternate destination, given the following restrictions:
At least one local mandatory destination is enabled.
The number of enabled destinations must meet the defined LOG_ARCHIVE_MIN_SUCCEED_DEST parameter value.
A destination cannot be its own alternate.
Increasing the number of enabled destinations decreases the number of available alternate archiving destinations.
When a destination fails, its alternate destination is enabled on the next archival operation. There is no support for enabling the alternate destination in the middle of the archival operation because that would require rereading already processed blocks. This is identical to the REOPENattribute behavior.
If the REOPEN attribute is specified with a nonzero value, the ALTERNATE attribute is ignored unless the MAX_FAILURE attribute has a nonzero value. If the MAX_FAILURE and REOPEN attributes have nonzero values and the failure count exceeds the specified failure threshold, theALTERNATE destination is enabled. Therefore, the ALTERNATE attribute does not conflict with a nonzero REOPEN attribute value.
In the sample initialization parameter file in
Example 15-1,
LOG_ARCHIVE_DEST_1 automatically fails over to the alternate destination
LOG_ARCHIVE_DEST_2 on the next archival operation if an error occurs or the device becomes full.
Example 15-1 Automatically Failing Over to an Alternate Destination
LOG_ARCHIVE_DEST_1='LOCATION=/disk1 MANDATORY MAX_FAILURE=1
ALTERNATE=LOG_ARCHIVE_DEST_2'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_2='LOCATION=/disk2 MANDATORY'
LOG_ARCHIVE_DEST_STATE_2=ALTERNATE
In both this example and in the following example, the MAX_FAILURE attribute must be specified or the destination will not fail over to the alternate destination when a problem is encountered. There is no default value for MAX_FAILURE; you must supply a value.
Example 15-2 Defining an Alternate Oracle Net Service Name to the Same Standby Database
This example shows how to define an alternate Oracle Net service name to the same standby database.
LOG_ARCHIVE_DEST_1='LOCATION=/disk1 MANDATORY MAX_FAILURE=1'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_2='SERVICE=stby1_path1 ALTERNATE=LOG_ARCHIVE_DEST_3'
LOG_ARCHIVE_DEST_STATE_2=ENABLE
LOG_ARCHIVE_DEST_3='SERVICE=stby1_path2'
LOG_ARCHIVE_DEST_STATE_3=ALTERNATE
COMPRESSION
The COMPRESSION attribute is used to specify whether redo data is compressed before transmission to a redo transport destination.
Note:
Redo transport compression is a feature of the Oracle Advanced Compression option. You must purchase a license for this option before using the redo transport compression feature.
The following example shows the COMPRESSION attribute with the LOG_ARCHIVE_DEST_n parameter.
LOG_ARCHIVE_DEST_3='SERVICE=denver SYNC COMPRESSION=ENABLE'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
DB_UNIQUE_NAME
Specifies a unique name for the database at this destination.
This attribute is optional if:
This attributes is required if the LOG_ARCHIVE_CONFIG=DG_CONFIG initialization parameter is specified and if this is a remote destination (specified with the SERVICE attribute).
Use the DB_UNIQUE_NAME attribute to clearly identify the relationship between a primary and standby databases. This attribute is particularly helpful if there are multiple standby databases in the Data Guard configuration.
The name specified by the DB_UNIQUE_NAME must match one of the DB_UNIQUE_NAME values in the DG_CONFIG list. Redo transport services validate that the DB_UNIQUE_NAME attribute of the database at the specified destination matches the DB_UNIQUE_NAME attribute or the connection to that destination is refused.
The name specified by the DB_UNIQUE_NAME attribute must match the name specified by the DB_UNIQUE_NAME initialization parameter of the database identified by the destination.
In the following example
, the
DB_UNIQUE_NAME parameter specifies
boston (
DB_UNIQUE_NAME=boston), which is also specified with the
DB_UNIQUE_NAME attribute on the
LOG_ARCHIVE_DEST_1 parameter. The
DB_UNIQUE_NAME attribute on the
LOG_ARCHIVE_DEST_2 parameter specifies the
chicago destination. Both
boston and
chicago are listed in the
LOG_ARCHIVE_CONFIG=DG_CONFIG parameter.
DB_UNIQUE_NAME=boston
LOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston,denver)'
LOG_ARCHIVE_DEST_1='LOCATION=/arch1/
VALID_FOR=(ALL_LOGFILES,ALL_ROLES)
DB_UNIQUE_NAME=boston'
LOG_ARCHIVE_DEST_2='SERVICE=Sales_DR
VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)
DB_UNIQUE_NAME=chicago'
DELAY
Specifies a minimum time lag between when redo data from the primary site is archived on a standby site and when the archived redo log file is applied to the standby database or any standbys cascaded from it.
The DELAY attribute is optional. By default there is no delay.
The DELAY attribute indicates the archived redo log files at the standby destination are not available for recovery until the specified time interval has expired. The time interval is expressed in minutes, and it starts when the redo data is successfully transmitted to, and archived at, the standby site.
The DELAY attribute may be used to protect a standby database from corrupted or erroneous primary data. However, there is a tradeoff because during failover it takes more time to apply all of the redo up to the point of corruption.
The DELAY attribute does not affect the transmittal of redo data to a standby destination.
If you have real-time apply enabled, any delay that you set will be ignored.
Changes to the DELAY attribute take effect the next time redo data is archived (after a log switch). In-progress archiving is not affected.
You can override the specified delay interval at the standby site, as follows:
For a physical standby database:
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE NODELAY;
For a logical standby database:
SQL> ALTER DATABASE START LOGICAL STANDBY APPLY NODELAY;
The DELAY value that a cascaded standby uses is the value that was set for the LOG_ARCHIVE_DEST_n parameter on the primary that shipped the redo to the cascading standby.
You can use the DELAY attribute to set up a configuration where multiple standby databases are maintained in varying degrees of synchronization with the primary database. However, this protection incurs some overhead during failover, because it takes Redo Apply more time to apply all the redo up to the corruption point.
For example, assume primary database A has standby databases B and C. Standby database B is set up as the disaster recovery database and therefore has no time lag. Standby database C is set up with a 2-hour delay, which is enough time to allow user errors to be discovered before they are propagated to the standby database.
The following example shows how to specify the DELAY attribute for this configuration:
LOG_ARCHIVE_DEST_1='LOCATION=/arch/dest MANDATORY'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_2='SERVICE=stbyB SYNC AFFIRM'
LOG_ARCHIVE_DEST_STATE_2=ENABLE
LOG_ARCHIVE_DEST_3='SERVICE=stbyC DELAY=120'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
Note:
Alternatively, you can use Flashback Database to revert the database to a point-in-time or SCN in a different database incarnation as long as there is sufficient flashback log data. Using Flashback Database is described in
Oracle Database Backup and Recovery User's Guide.
LOCATION and SERVICE
Each destination must specify either the LOCATION or the SERVICE attribute to identify either a local disk directory or a remote database destination where redo transport services can transmit redo data.
LOG_ARCHIVE_DEST_1 through LOG_ARCHIVE_DEST_10 destinations can contain either a LOCATION attribute or a SERVICE attribute.
LOG_ARCHIVE_DEST_11 through LOG_ARCHIVE_DEST_31 destinations can only contain a SERVICE attribute.
Either the LOCATION or the SERVICE attribute must be specified. There is no default.
The LOG_ARCHIVE_DEST_11 through LOG_ARCHIVE_DEST_31 parameters do not support the LOCATION attribute.
If you are specifying multiple attributes, specify the LOCATION or SERVICE attribute first in the list of attributes.
You must specify at least one local disk directory with the LOCATION attribute. This ensures that local archived redo log files are accessible should media recovery of a database be necessary. You can specify up to thirty additional local or remote destinations.
For the LOCATION attribute, you can specify one of the following:
LOCATION=local_disk_directory
This specifies a unique directory path name for a disk directory on the system that hosts the database. This is the local destination for archived redo log files.
LOCATION=USE_DB_RECOVERY_FILE_DEST
To configure a fast recovery area, specify the directory or Oracle Storage Manager disk group that will serve as the fast recovery area using the
DB_RECOVERY_FILE_DEST initialization parameter. For more information about fast recovery areas, see
Oracle Database Backup and Recovery User's Guide.
When you specify a SERVICE attribute:
You identify remote destinations by specifying the SERVICE attribute with a valid Oracle Net service name (SERVICE=net_service_name) that identifies the remote Oracle database instance to which the redo data will be sent.
The Oracle Net service name that you specify with the SERVICE attribute is translated into a connection descriptor that contains the information necessary for connecting to the remote database.
Transmitting redo data to a remote destination requires a network connection and an Oracle database instance associated with the remote destination to receive the incoming redo data.
To verify the current settings for LOCATION and SERVICE attributes, query the V$ARCHIVE_DEST fixed view:
The TARGET column identifies if the destination is local or remote to the primary database.
The DESTINATION column identifies the values that were specified for a destination. For example, the destination parameter value specifies the Oracle Net service name identifying the remote Oracle instance where the archived redo log files are located.
- Example 1 Specifying the LOCATION Attribute
LOG_ARCHIVE_DEST_2='LOCATION=/disk1/oracle/oradata/payroll/arch/'
LOG_ARCHIVE_DEST_STATE_2=ENABLE
- Example 2 Specifying the SERVICE Attribute
LOG_ARCHIVE_DEST_3='SERVICE=stby1'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
MANDATORY
Specifies that filled online log files must be successfully archived to the destination before they can be reused.
The LOG_ARCHIVE_DEST_11 through LOG_ARCHIVE_DEST_31 parameters do not support the MANDATORY attribute.
If MANDATORY is not specified, then, by default, the destination is considered to be optional.
At least one destination must succeed, even if all destinations are optional. If archiving to an optional destination fails, the online redo log file is still available for reuse and may be overwritten eventually. However, if the archival operation of a mandatory destination fails, online redo log files cannot be overwritten.
The
LOG_ARCHIVE_MIN_SUCCEED_DEST=n parameter (where
n is an integer from 1 to 10) specifies the number of destinations that must archive successfully before online redo log files can be overwritten.
All MANDATORY destinations and optional local destinations contribute to satisfying the LOG_ARCHIVE_MIN_SUCCEED_DEST=n count. If the value set for the LOG_ARCHIVE_MIN_SUCCEED_DEST parameter is met, the online redo log file is available for reuse. For example, you can set the parameter as follows:
# Database must archive to at least two locations before
# overwriting the online redo log files.
LOG_ARCHIVE_MIN_SUCCEED_DEST = 2
You must have at least one local destination, which you can declare MANDATORY or leave as optional.
At least one local destination is operationally treated as mandatory, because the minimum value for the LOG_ARCHIVE_MIN_SUCCEED_DESTparameter is 1.
The failure of any mandatory destination makes the LOG_ARCHIVE_MIN_SUCCEED_DEST parameter irrelevant.
The LOG_ARCHIVE_MIN_SUCCEED_DEST parameter value cannot be greater than the number of mandatory destinations plus the number of optional local destinations.
The BINDING column of the V$ARCHIVE_DEST fixed view specifies how failure affects the archival operation
The following example shows the MANDATORY attribute:
LOG_ARCHIVE_DEST_1='LOCATION=/arch/dest MANDATORY'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_3='SERVICE=denver MANDATORY'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
MAX_CONNECTIONS
Enables multiple network connections to be used when sending an archived redo log file to a redo transport destination. Using multiple network connections can improve redo transport performance over high-latency network links.
The MAX_CONNECTIONS attribute is optional. If it is specified, it is only used when redo transport services use ARCn processes for archival.
If MAX_CONNECTIONS is set to 1 (the default), redo transport services use a single ARCn process to transmit redo data to the remote destination.
If MAX_CONNECTIONS is set to a value greater than 1, redo transport services use multiple ARCn processes to transmit redo in parallel to archived redo log files at the remote destination. Each archiver (ARCn) process uses a separate network connection.
With multiple ARCn processes, redo transmission occurs in parallel, thus increasing the speed at which redo is transmitted to the remote destination.
Redo that is received from an ARCn process is written directly to an archived redo log file. Therefore, it cannot be applied in real-time as it is received.
The actual number of archiver processes in use at any given time may vary based on the archiver workload and the value of the
LOG_ARCHIVE_MAX_PROCESSES initialization parameter. For example, if the total of
MAX_CONNECTIONS attributes on all destinations exceeds the value of
LOG_ARCHIVE_MAX_PROCESSES, then Data Guard will use as many ARC
n processes as possible, but the number may be less than what is specified by the
MAX_CONNECTIONS attribute.
When using multiple
ARC
n processes in an Oracle RAC environment, configure the primary instance to transport redo data to a single standby database instance. If redo transport services are not configured as such, then archival will return to the default behavior for remote archival, which is to transport redo data using a single ARC
n process.
The following example shows the MAX_CONNECTIONS attribute:
LOG_ARCHIVE_DEST_1='LOCATION=/arch/dest'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
LOG_ARCHIVE_DEST_3='SERVICE=denver MAX_CONNECTIONS=3'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
MAX_FAILURE
Controls the consecutive number of times redo transport services attempt to reestablish communication and transmit redo data to a failed destination before the primary database gives up on the destination.
The MAX_FAILURE attribute is optional. By default, there are an unlimited number of archival attempts to the failed destination.
This attribute is useful for providing failure resolution for destinations to which you want to retry transmitting redo data after a failure, but not retry indefinitely.
When you specify the MAX_FAILURE attribute, you must also set the REOPEN attribute. Once the specified number of consecutive attempts is exceeded, the destination is treated as if the REOPEN attribute was not specified.
You can view the failure count in the FAILURE_COUNT column of the V$ARCHIVE_DEST fixed view. The related column REOPEN_SECS identifies theREOPEN attribute value.
Note:
Once the failure count for the destination reaches the specified
MAX_FAILURE attribute value, the only way to reuse the destination is to modify the
MAX_FAILURE attribute value or any attribute. This has the effect of resetting the failure count to zero (0).
The failure count is reset to zero (0) whenever the destination is modified by an ALTER SYSTEM SET statement. This avoids the problem of setting the MAX_FAILURE attribute to a value less than the current failure count value.
Once the failure count is greater than or equal to the value set for the MAX_FAILURE attribute, the REOPEN attribute value is implicitly set to zero, which causes redo transport services to transport redo data to an alternate destination (defined with the ALTERNATE attribute) on the next archival operation.
Redo transport services attempt to archive to the failed destination indefinitely if you do not specify the MAX_FAILURE attribute (or if you specifyMAX_FAILURE=0), and you specify a nonzero value for the REOPEN attribute. If the destination has the MANDATORY attribute, the online redo log file is not reusable until it has been archived to this destination.
The following example allows redo transport services up to three consecutive archival attempts, tried every 5 seconds, to the arc_dest destination. If the archival operation fails after the third attempt, the destination is treated as if the REOPEN attribute was not specified.
LOG_ARCHIVE_DEST_1='LOCATION=/arc_dest REOPEN=5 MAX_FAILURE=3'
LOG_ARCHIVE_DEST_STATE_1=ENABLE
NET_TIMEOUT
Specifies the number of seconds that the LGWR background process will block waiting for a redo transport destination to acknowledge redo data sent to it. If an acknowledgement is not received within NET_TIMEOUT seconds, an error is logged and the redo transport session to that destination is terminated.
The
NET_TIMEOUT attribute is optional. However, if you do not specify the
NET_TIMEOUT attribute it will be set to 30 seconds, but the
primary database can potentially stall. To avoid this situation, specify a small, nonzero value for the
NET_TIMEOUT attribute so the primary database can continue operation after the user-specified timeout interval expires when waiting for status from the network server.
The following example shows how to specify a 10-second network timeout value on the primary database with the NET_TIMEOUT attribute.
LOG_ARCHIVE_DEST_2='SERVICE=stby1 SYNC NET_TIMEOUT=10'
LOG_ARCHIVE_DEST_STATE_2=ENABLE
NOREGISTER
Indicates that the location of the archived redo log file should not be recorded at the corresponding destination.
The NOREGISTER attribute is optional if the standby database destination is a part of a Data Guard configuration.
The NOREGISTER attribute is required if the destination is not part of a Data Guard configuration.
This attribute pertains to remote destinations only. The location of each archived redo log file is always recorded in the primary database control file.
The following example shows the NOREGISTER attribute:
LOG_ARCHIVE_DEST_5='NOREGISTER'
REOPEN
Specifies the minimum number of seconds before redo transport services should try to reopen a failed destination.
The REOPEN attribute is optional.
Redo transport services attempt to reopen failed destinations at log switch time.
Redo transport services check if the time of the last error plus the REOPEN interval is less than the current time. If it is, redo transport services attempt to reopen the destination.
REOPEN applies to all errors, not just connection failures. These errors include, but are not limited to, network failures, disk errors, and quota exceptions.
If you specify REOPEN for an optional destination, it is possible for the Oracle database to overwrite online redo log files if there is an error. If you specify REOPEN for a MANDATORY destination, redo transport services will stall the primary database when it is not possible to successfully transmit redo data. When this situation occurs, consider the following options:
Change the destination by deferring the destination, specifying the destination as optional, or changing the SERVICE attribute value.
Specify an alternate destination.
Disable the destination.
The following example shows the REOPEN attribute.
LOG_ARCHIVE_DEST_3='SERVICE=stby1 MANDATORY REOPEN=60'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
SYNC and ASYNC
Specifies whether the synchronous (
SYNC) or asynchronous (
ASYNC) redo transport mode is to be used.
The LOG_ARCHIVE_DEST_11 through LOG_ARCHIVE_DEST_31 parameters do not support the SYNC attribute.
The redo data generated by a transaction must have been received by every enabled destination that has the SYNC attribute before that transaction can commit.
The redo data generated by a transaction need not have been received at a destination that has the ASYNC attribute before that transaction can commit. This is the default behavior if neither SYNC or ASYNC is specified.
The following example shows the SYNC attribute with the LOG_ARCHIVE_DEST_n parameter.
LOG_ARCHIVE_DEST_3='SERVICE=stby1 SYNC'
LOG_ARCHIVE_DEST_STATE_3=ENABLE
TEMPLATE
Defines a directory specification and format template for names of archived redo log files at the destination. The template is used to generate a filename that is different from the default filename format defined by the LOG_ARCHIVE_FORMAT initialization parameter at the redo destination.
The TEMPLATE attribute is optional. If TEMPLATE is not specified, archived redo logs are named using the value of the LOG_ARCHIVE_FORMATinitialization parameter.
The TEMPLATE attribute overrides the LOG_ARCHIVE_FORMAT initialization parameter setting at the remote archival destination.
The TEMPLATE attribute is valid only with remote destinations (that is, destinations specified with the SERVICE attribute).
The value you specify for filename_template must contain the %s, %t, and %r directives described in
Table 15-1.
The filename_template value is transmitted to the destination, where it is translated and validated before creating the filename.
VALID_FOR
Specifies whether redo data will be written to a destination, based on the following factors:
Whether the database is currently running in the primary or the standby role
Whether online redo log files, standby redo log files, or both are currently being archived on the database at this destination
The VALID_FOR attribute is optional. However, Oracle recommends that the VALID_FOR attribute be specified for each redo transport destination at each database in a Data Guard configuration so that redo transport continues after a role transition to any standby database in the configuration.
To configure these factors for each LOG_ARCHIVE_DEST_n destination, you specify this attribute with a pair of keywords: VALID_FOR=(redo_log_type,database_role):
If you do not specify the VALID_FOR attribute for a destination, by default, archiving online redo log files and standby redo log files is enabled at the destination, regardless of whether the database is running in the primary or the standby role. This default behavior is equivalent to setting the(ALL_LOGFILES,ALL_ROLES) keyword pair on the VALID_FOR attribute.
The VALID_FOR attribute enables you to use the same initialization parameter file for both the primary and standby roles.
The following example shows the default VALID_FOR keyword pair:
LOG_ARCHIVE_DEST_1='LOCATION=/disk1/oracle/oradata VALID_FOR=(ALL_LOGFILES, ALL_ROLES)'
When this database is running in either the primary or standby role, destination 1 archives all log files to the /disk1/oracle/oradata local directory location.
