Optional attributes of the OracleDataGuardLOG_ARCHIVE_DEST_n Parameter

In the routine configuration process of oracledatabasepolicuard, set affsert, noaffrem, DB_UNIQUE_NAME, DELAY, L in the LOG_ARCHIVE_DEST_n initialization parameter.

In the routine configuration process of Oracle Database Data Guard, set affsert, noaffrem, DB_UNIQUE_NAME, DELAY, L in the LOG_ARCHIVE_DEST_n initialization parameter.

In the routine configuration process of Oracle Database Data Guard, set affsert, noaffrem, DB_UNIQUE_NAME, DELAY, LOCATION, SERVICE, SYNC, ASYNC in the LOG_ARCHIVE_DEST_n initialization parameter, the VALID_FOR attribute can meet most application scenarios. You can also consider this parameter as a required parameter. This article will discuss some other optional attributes of LOG_ARCHIVE_DEST_n Based on 11gR2, which will help us gain a deeper understanding of the working principles and details of Oracle Data Guard. At the same time, this article is a supplement to the chapter DG discussed in my book.

1. ALTERNATE attributes

When the initial destination fails, this parameter is used to specify a rotation archiving destination. This attribute does not support LOG_ARCHIVE_DEST_11 to LOG_ARCHIVE_DEST_31 Redo destination settings.

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

You can use V $ ARCHIVE_DEST.STATUS to view information about the ALTERNATE destination.

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

Only one ALTERNATE destination can be specified for each LOG_ARCHIVE_DEST_n initialization parameter, but multiple LOG_ARCHIVE_DEST_n initialization parameters share the same ALTERNATE destination.

Avoid using the same disk or network as the primary destination, and avoid the ALTERNATE destination being invalid when the primary destination is invalid.

If the referenced location of LOG_ARCHIVE_DEST_n is not specified, the ALTERNATE destination implies a delay (DEFER). Similarly, you can use alter system to enable or delay the ALTERNATE destination at runtime.

You can increase the number of archiving destinations to reduce the number of active ALTERNATE archiving destinations.

When the archive destination fails, the ALTERNATE destination is enabled for the next archive operation. The ALTERNATE destination cannot be enabled during the archive operation. Because the REOPEN attribute requires you to re-read the blocks processed by the destination.

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

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 Oracle Net Service name of the ALTERNATE destination 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

2. COMPRESSION attributes

The COMPRESSION attribute indicates whether to compress the REDO data before it is transmitted to the REDO transmission destination.

Redo transmission Compression is a feature of the Oracle Advanced Compression component. You must purchase the license for this option before using this feature.

COMPRESSION = ENABLE or DISABLE. The default value is DISABLE.

Query the V $ ARCHIVE_DEST.COMPRESSION field to determine whether compression is enabled.

The following example shows the COMPRESSION attribute in the LOG_ARCHIVE_DEST_n parameter:

LOG_ARCHIVE_DEST_3 = 'service = denver sync compression = enable'

LOG_ARCHIVE_DEST_STATE_3 = ENABLE

3. MANDATORY attributes

The MANDATORY attribute indicates that the filled online log files must be archived to the destination before they can be reused.

You can use the V $ ARCHIVE_DEST.BINDING field to check whether this parameter is specified.

The MANDATORY attribute is not supported in the initialization parameters from LOG_ARCHIVE_DEST_11 to LOG_ARCHIVE_DEST_31.

Even if all archiving destinations are optional, at least one Archiving destination must be successful. If archiving fails to an optional destination, the online Redo log file may be reused and eventually overwritten. However, if you fail to archive a MANDATORY destination, the online Redo log file cannot be overwritten.

LOG_ARCHIVE_MIN_SUCCEED_DEST = n initialization parameter (n is an integer ranging from 1 to 10). This parameter specifies the number of destinations that must be archived before the online Redo log file is overwritten.

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

# Database must archive to at least two locations before

# Overwriting the online redo log files.

LOG_ARCHIVE_MIN_SUCCEED_DEST = 2

The database must have at least one local destination. You can define MANDATORY or retain it as an optional destination. At least one local destination is set to MANDATORY because the minimum value of the LOG_ARCHIVE_MIN_SUCCESSD_DEST parameter is 1.

The value of LOG_ARCHIVE_MIN_SUCCEED_DEST cannot be greater than the MANDATORY destination and the number of optional local destinations.

The V $ ARCHIVE_DEST.BINDING field indicates what kind of failure does not affect the archiving 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

4. MAX_CONNECTIONS attributes

Enable multiple network connections when sending an archived Redo log file to the Redo transmission destination. Using multiple network connections can improve the Redo Transmission Performance in High-latency network connections.

The default value is 1 and the value range is 1 to 20.

You can obtain the value settings of this parameter by querying the V $ ARCHIVE_DEST.MAX_CONNECTIONS field of the primary database.

If this parameter is specified, it is used only when the Redo Transmission Service uses the ARCn process for archiving.

If MAX_CONNECTIONS is set to 1 (default), Redo transmission uses a single ARCn process to transmit Redo data to a remote destination.

If the value set by MAX_CONNECTIONS is greater than 1, Redo transmission uses multiple ARCn processes to concurrently transmit Redo logs to remote destinations for archiving. Each archiving process uses an independent network connection.

The Redo data is received from the ARCn process and directly written to the archive Redo log file. Therefore, this attribute cannot be applied to real-time log applications.

The actual number of archive processes used may be different at different times. This is determined by the archiving load and LOG_ARCHIVE_MAX_PROCESSES initialization. The total number of archive processes is limited by LOG_ARCHIVE_MAX_PROCESSES.

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

5. MAX_FAILURE attributes

This attribute controls the number of times Redo data is transmitted to the failed destination before the master database abandons the destination.

No default value. The correct value is> = 0.

The REOPEN attribute is required. view the MAX_FAILURE, FAILURE_COUNT, and REOPEN_SECS fields of the V $ ARCHIVE_DEST view to view the relevant information.

By default, Oracle does not limit the number of failed archiving destinations.

This attribute is useful for solving the failure destination problem, so that you can try to transmit Redo data to other destinations after the failure, rather than waiting for a long time.

When the MAX_FAILURE attribute is specified, the REOPEN attribute must be set. Once the specified number of consecutive attempts is exceeded, the destination is treated as not specified REOPEN.

You can use the V $ ARCHIVE_DEST.FAILURE_COUNT field to view the number of failures and the REOPEN_SECS field to identify the value of the REOPEN attribute.

Once the destination fails to reach the specified MAX_FAILURE attribute value, there is only one way to re-use the destination and modify the MAX_FAILURE attribute value or any other attribute. This will reset the failure count to 0.

No matter when the destination parameter fails to be modified using the alter system set statement, it is reset to 0 to prevent setting a MAX_FAILURE attribute value that is less than the current failure count.

Once the number of failures is greater than or equal to the set MAX_FAILURE attribute value, the REOPEN attribute value is secretly set to 0, which will cause the Redo transmission service to transmit Redo data to an ALTERNATE destination during the next archiving operation.