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  Oracle Data Guard LOG_ARCHIVE_DEST_n optional attribute parameters
     
  Add Date : 2017-04-13      
         
         
         
  In Oracle Database Data Guard configuration routine, set LOG_ARCHIVE_DEST_n initialization parameters AFFIRM, NOAFFIRM, DB_UNIQUE_NAME, DELAY, LOCATION, SERVICE, SYNC, ASYNC, VALID_FOR property can meet most application scenarios, can also be considered part of this argument is Required parameter. This article will discuss some of the other optional attributes LOG_ARCHIVE_DEST_n 11gR2 based documents, this part of the property will help us to a deeper understanding of Oracle Data Guard works and details of the work. At the same time, this article is to discuss in my book supplement DG chapter.

1.ALTERNATE property

When the initial destination fails, use this parameter to specify a rotation archive destination. This attribute is not supported LOG_ARCHIVE_DEST_11 to LOG_ARCHIVE_DEST_31 Redo destination setting.

ALTERNATE = LOG_ARCHIVE_DEST_n, LOG_ARCHIVE_DEST_n is a destination, n is a value from 1 to 10.

Through V $ ARCHIVE_DEST.STATUS you can view ALTERNATE destination information.

If the REOPEN attribute is specified as a nonzero value, ALTERNATE attribute is ignored unless MAX_FAILURE attribute is also designated as a non-zero value, so if the number of failures exceeds the specified failure threshold (MAX_FAILURE), ALTERNATE destination is enabled, Thus, ALTERNATE attribute does not conflict with a nonzero REOPEN attribute value.

You can only specify a destination ALTERNATE LOG_ARCHIVE_DEST_n initialization parameter for each, but more than LOG_ARCHIVE_DEST_n initialization parameters share the same ALTERNATE destination.

Avoid specifying the ALTERNATE destination is the primary destination using the same disk or network, when the primary destination to avoid invalid result ALTERNATE destination is also invalid.

If you do not specify the location of LOG_ARCHIVE_DEST_n quoted, the ALTERNATE destination is delayed implied (DEFER), also at run time can be enabled or delayed (DEFER) ALTERNATE destination using the ALTER SYSTEM.

By increasing the number of destinations archiving to reduce the number of activities ALTERNATE archive destination.

When the archive destination fails, ALTERNATE destination is enabled for the next archive operation here does not support the ALTERNATE destination is enabled during an archive operation. Because the behavior REOPEN attribute requirements to re-read the destination block already processed.

The following example shows that if an error occurs or the disk is full, the next archive operation from LOG_ARCHIVE_DEST_1 automatically FAILOVER to ALTERNATE destination LOG_ARCHIVE_DETS_2 performed.

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

The following example shows how to set the ALTERNATE destination Oracle Net Service name, assigned to the same database STANDBY:

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

2.COMPRESSION property

COMPRESSION attribute is used to indicate whether the data prior to transmission to the REDO REDO transfer destination is compressed.

Redo transport compression is a feature of Oracle Advanced Compression component, then you must buy the license for the option to use this feature.

COMPRESSION = ENABLE or DISABLE, the default is DISABLE.

By querying the V $ ARCHIVE_DEST.COMPRESSION the field can determine whether compression is enabled.

The following example shows LOG_ARCHIVE_DEST_n parameters COMPRESSION properties:

LOG_ARCHIVE_DEST_3 = 'SERVICE = denver SYNC COMPRESSION = ENABLE'

LOG_ARCHIVE_DEST_STATE_3 = ENABLE

3.MANDATORY property

After the online log file MANDATORY attribute specified must be filled successfully archived to the destination in order to be reused.

Through V $ ARCHIVE_DEST.BINDING field to see if this parameter is specified.

LOG_ARCHIVE_DEST_11 to LOG_ARCHIVE_DEST_31 initialization parameter is not supported MANDATORY attribute.

Even if all of the archive destination is optional, at least one archive destination must succeed. If the archive to an optional destination fails, online Redo log files may be reused, may eventually be overwritten. However, if the archive operation a MANDATORY destination fails, online Redo log file can not be overwritten.

LOG_ARCHIVE_MIN_SUCCEED_DEST = n initialization parameter (n is an integer ranging from 1 to 10), which specifies the Online Redo log files before they are overwritten, the number of destinations to be successful archiving.

All MANDATORY destinations and optional local destinations to help meet LOG_ARCHIVE_MIN_SUCCESSD_DEST = number n.

# Database must archive to at least two locations before

# Overwriting the online redo log files.

LOG_ARCHIVE_MIN_SUCCEED_DEST = 2

Database must have at least one local destination, you can define MANDATORY or reserved optional destination. At least one local minimum value because the destination is set MANDATORY LOG_ARCHIVE_MIN_SUCCESSD_DEST parameter is 1.

LOG_ARCHIVE_MIN_SUCCEED_DEST parameter value can not be greater than MANDATORY destinations plus the number of optional local destinations.

V $ ARCHIVE_DEST.BINDING field indicates what kind of failure does not affect the operation of the archive.

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

4.MAX_CONNECTIONS property

Sending an archive log files Redo Redo the transfer destination to enable multiple network connection, use multiple network connections can improve Redo transmission in a high-latency network connection performance.

The default value is 1, the range of values is 1-20.

Through V $ ARCHIVE_DEST.MAX_CONNECTIONS field queries the primary database to set the parameter value can be obtained.

If you specify this parameter, only when Redo transport services use ARCn archiving process time will be used.

If MAX_CONNECTIONS set to 1 (default), Redo transport services use a single transmission Redo ARCn process data to the remote destination.

If the value is greater than the set MAX_CONNECTIONS 1, Redo transport services use multiple processes ARCn parallel transmission to a remote destination Redo Redo archive log files. Each archiving process using a separate network connection.

Redo data is received from ARCn process, write directly to the archive Redo log file, so that the property can not be applied in real-time log application.

In the real number of archive processes used at different times may be different, which is based on archive load and LOG_ARCHIVE_MAX_PROCESSES initialization to determine the total number of archiving processes by LOG_ARCHIVE_MAX_PROCESSES restrictions.

The following example shows MAX_CONNECTIONS properties:

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

5.MAX_FAILURE property

This attribute controls Redo transport service continuous attempts to re-establish the connection, the number of times before the primary database abandon Redo data transmission destination to destination failed.

There is no default value, the correct value is> = 0.

Requirements REOPEN attribute view V $ ARCHIVE_DEST view MAX_FAILURE, FAILURE_COUNT, REOPEN_SECS field view related information.

By default, Oracle does not limit the number of failed attempts archive destination.

This property is a destination of failure to solve the problem is useful, it can be made after a failed attempt to transfer data to other destinations Redo instead of waiting for the foreseeable future.

When you specify MAX_FAILURE property, you must set the REOPEN attribute. Once a specified number of consecutive attempts is exceeded, the destination is treated as not specified REOPEN for processing.

Times by V $ ARCHIVE_DEST.FAILURE_COUNT field view failed, values REOPEN_SECS field identifies the REOPEN attribute.

Once the destination number of failed arrival MAX_FAILURE specified attribute values, only one way to reuse the destination, modify MAX_FAILURE property value, or any other property, which will reset the failure count to zero.

At any time, modify the destination parameters ALTER SYSTEM SET statement failures will be reset to 0, which is to prevent a set smaller than the current number of failed MAX_FAILURE property values.

Should it fail MAX_FAILURE attribute value equal to or greater than the number set, REOPEN attribute value is implicitly set to 0, which will cause the next time archiving operations, Redo Redo data transmission service delivery to a destination ALTERNATE.

If no MAX_FAILURE attribute (or set MAX_FAILORE = 0), and specify a nonzero value for the REOPEN attribute, Redo transport services in the foreseeable future to the failed attempt to archive destination. If the destination is set MANDATORY attribute, the online Redo log file can not be reused until the online Redo log files are successfully archived to the destination.

The following example allows Redo log transport services archive 3 consecutive attempts, retrying every 5 seconds to arc_dest destination. If the archive operation three failed attempts, the destination is treated as REOPEN attribute is not specified for processing.

LOG_ARCHIVE_DEST_1 = 'LOCATION = / arc_dest REOPEN = 5 MAX_FAILURE = 3'

LOG_ARCHIVE_DEST_STATE_1 = ENABLE

6.NET_TIMEOUT property

Specifies the background process LGWR wait Redo Redo the number of seconds to acknowledge receipt of the transmission destination data, if confirmation is not received within NET_TIMEOUT seconds, an error is recorded at the same time to the destination Redo transport sessions are interrupted.

The default is 30 seconds, the range of values 1-1200.

This parameter specifies the SYNC attribute must be specified.

By primary database query V $ ARCHIVE_DEST.NET_TIMEOUT field to view the value of the property.

Although the minimum allowable value NET_TIMEOUT 1 second, Oracle recommends a minimum value in 8-10 seconds, to prevent instantaneous of network errors disconnected Standby database.

The following example shows how to use NET_TIMETOUT property set network timeout value of 10 seconds in the primary database:

LOG_ARCHIVE_DEST_2 = 'SERVICE = stby1 SYNC NET_TIMEOUT = 10'

LOG_ARCHIVE_DEST_STATE_2 = ENABLE

7.REOPEN property

This attribute specifies Redo transport services attempt to reopen failed destinations minimum number of seconds to wait.

The default value is 300 seconds, the value should be greater than 0.

By REOPEN_SECS and MAX_FAILURE field V $ ARCHIVE_DEST view you can obtain the relevant information.

Redo transport services attempt to reopen failed destinations at log switch.

Redo transport service to check if the last error plus the REOPEN interval is less than the current time period, 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 failure, disk failure, abnormal and permissions.

If you specify REOPEN destination is optional, if there are any errors, Oracle database is likely to cover online Redo log file, if you specify REOPEN for MANDATORY destination, when data can not be successfully transmitted Redo, Redo transport services may delay the main database . When this happens, consider the following options:

a). The delay destination, specify the destination as optional destinations, change or SERVICE attribute value.

b). specify the ALTERNATE destination.

c). 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

8.TEMPLATE property

At the destination of the Redo log file name and define specific directory format template, template parameters for generating LOG_ARCHIVE_FORMAT Redo destination initialization parameter format defined by a different file name.

By querying the V $ ARCHIVE_DEST of REMOTE_TEMPLATE and REGISTER fields you can query information.

If not specified TEMPLATE, archiving Redo log usage value LOG_ARCHIVE_FORMAT initialization parameter named.

TEMPLATE attribute is only valid (specified by the destination SERVICE attribute) to the remote destination.

The specified file name template must contain% s,% t, and% r directives:

% T thread instance number.

% T instance thread number, filled with zeros.

% S log file sequence number.

% S log file sequence number, filled with zeros.

% R resetlogs ID.

% R resetlogs ID, filled with zeros.

filename_template value is transferred to the destination, before creating a file name for transmission and verification.
     
         
         
         
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