合 DG参数 LOG_ARCHIVE_DEST_n

This chapter provides reference information for the attributes of the LOG_ARCHIVEDESTn initialization parameter. The following list shows the attributes:

AFFIRM and NOAFFIRM
ALTERNATE
COMPRESSION
DB_UNIQUE_NAME
DELAY
LOCATION and SERVICE
MANDATORY
MAX_CONNECTIONS
MAX_FAILURE
NET_TIMEOUT
NOREGISTER
REOPEN
SYNC and ASYNC
VALID_FOR

Each LOG_ARCHIVEDESTn destination must contain either a LOCATION or SERVICE attribute to specify a local disk directory or a remotely accessed database, respectively. All other attributes are optional.

Note:

Several attributes of the LOG_ARCHIVEDESTn initialization parameter have been deprecated. These attributes are supported for backward compatibility only and are documented in theOracle Database Reference.

See Also:

Chapter 6 for more information about defining LOG_ARCHIVEDESTn destinations and setting up redo transport services

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.

Usage Notes

• If neither the AFFIRM nor the NOAFFIRM attribute is specified, the default is AFFIRM when the SYNC attribute is specified and NOAFFIRM when the ASYNC attribute is specified.
• Specification of the AFFIRM attribute without the SYNC attribute is deprecated and will not be supported in future releases.

See also:

SYNC and ASYNC attributes

Examples

The following example shows the AFFIRM attribute for a remote destination.

ALTERNATE

Specifies an alternate archiving destination to be used when the original destination fails.

Footnote 1 If the REOPEN attribute is specified with a nonzero value, the ALTERNATE attribute is ignored. If the MAX_FAILURE attribute is also specified with a nonzero value, and the failure count exceeds the specified failure threshold, the ALTERNATE destination is enabled. Therefore, the ALTERNATE attribute does not conflict with a nonzero REOPEN attribute value.

Usage Notes

• 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_ARCHIVEDESTn parameter, but several enabled destinations can share the same alternate destination.
• Ideally, an alternate destination should specify either:
  • A different disk location on the same local standby database system (shown in Example 15-1)
  • A different network route to the same standby database system (shown in Example 15-2)
  • A remote standby database system that closely mirrors that of the enabled destination
• 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 either 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 REOPEN attribute 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, the ALTERNATE destination is enabled. Therefore, the ALTERNATE attribute does not conflict with a nonzero REOPENattribute value.

Examples

In the sample initialization parameter file in Example 15-1, LOG_ARCHIVE_DEST_1 automatically fails over to 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

Notice in the example that a destination can also be in the ALTERNATE state, as specified with the LOG_ARCHIVE_DESTSTATEn initialization parameter. The ALTERNATE state defers redo transport services from transmitting redo data to this destination until such time as another destination failure automatically enables this destination.

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.

COMPRESSION

The COMPRESSION attribute is used to specify whether redo data is transmitted to a redo transport destination in compressed form or uncompressed form when resolving redo data gaps.

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.

Usage Notes

• The COMPRESSION attribute is optional. If it is not specified, the default compression behavior is DISABLE.

Example

The following example shows the COMPRESSION attribute with the LOG_ARCHIVEDESTn parameter.

DB_UNIQUE_NAME

Specifies a unique name for the database at this destination.

Usage Notes

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