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As explained in Oracle Database Concepts, Oracle Flashback Technology complements your physical backup and recovery strategy. This set of features provides an additional layer of data protection. Specifically, you can use the various features of Oracle Flashback to view past states of data and rewind your database without restoring backups or performing point-in-time recovery. In general, flashback features are more efficient and less disruptive than media recovery in most situations in which they apply.

如Oracle數(shù)據(jù)庫概念中所述哆键，Oracle Flashback技術(shù)補(bǔ)充了物理備份和恢復(fù)策略。 這組功能提供了一個(gè)額外的數(shù)據(jù)保護(hù)層瘦锹。 具體來說籍嘹，您可以使用Oracle Flashback的各種功能查看數(shù)據(jù)的過去狀態(tài)并回滾數(shù)據(jù)庫，而無需恢復(fù)備份或執(zhí)行時(shí)間點(diǎn)恢復(fù)弯院。 一般來說辱士，在大多數(shù)情況下，閃回功能比介質(zhì)恢復(fù)更高效听绳，更少破壞性颂碘。

Oracle Flashback Technology enables you to use the following functionality:
? Logical Flashback Features
? Flashback Database
Oracle閃回技術(shù)使您能夠使用以下功能：
? 邏輯閃回特性
? 閃回?cái)?shù)據(jù)庫

Logical Flashback Features
Most of the flashback features of Oracle operate at the logical level, enabling you to view and manipulate database objects. The logical-level flashback features of Oracle do not depend on RMAN and are available whether or not RMAN is part of your backup strategy. Except for Oracle Flashback Drop, the logical flashback features rely on undo data, which are records of the effects of each database update and the values overwritten in the update.

Oracle的大多數(shù)閃回功能在邏輯級(jí)運(yùn)行，使您能夠查看和操作數(shù)據(jù)庫對象椅挣。 Oracle的邏輯級(jí)閃回功能不依賴于RMAN凭涂，并且無論RMAN是否是備份策略的一部分，都是可用的贴妻。 除了Oracle Flashback Drop切油，邏輯閃回功能依賴于撤銷數(shù)據(jù)，記錄了每個(gè)數(shù)據(jù)庫更新所影響的記錄和在更新時(shí)重寫的數(shù)值名惩。

Oracle Database includes the following logical flashback features:

Oracle數(shù)據(jù)庫包括以下邏輯閃回功能：

? Oracle Flashback Query
You can specify a target time and run queries against a database, viewing results as
they would appear at the target time. To recover from an unwanted change like an
update to a table, you could choose a target time before the error and run a query
to retrieve the contents of the lost rows. Oracle Database Development Guide explains how to use this feature.

您可以指定目標(biāo)時(shí)間并對數(shù)據(jù)庫運(yùn)行查詢澎胡，查看在目標(biāo)時(shí)間顯示的結(jié)果。 要從不需要的更改（如更新表）中恢復(fù)娩鹉，可以選擇錯(cuò)誤之前的目標(biāo)時(shí)間攻谁，然后運(yùn)行查詢以檢索丟失行的內(nèi)容。 Oracle數(shù)據(jù)庫開發(fā)指南解釋了如何使用此功能弯予。

? Oracle Flashback Version Query
You can view all versions of all rows that ever existed in one or more tables in a
specified time interval. You can also retrieve metadata about the differing versions
of the rows, including start and end time, operation, and transaction ID of the
transaction that created the version. You can use this feature to recover lost data
values and to audit changes to the tables queried. Oracle Database Development Guide explains how to use this feature.

您可以在指定的時(shí)間間隔中查看一個(gè)或多個(gè)表中存在的所有行的所有版本戚宦。 您還可以檢索有關(guān)行的不同版本的元數(shù)據(jù)，包括創(chuàng)建版本的事務(wù)的開始和結(jié)束時(shí)間锈嫩，操作和事務(wù)ID受楼。 您可以使用此功能恢復(fù)丟失的數(shù)據(jù)值，并審計(jì)對所查詢的表的更改呼寸。Oracle數(shù)據(jù)庫開發(fā)指南解釋了如何使用此功能艳汽。

? Oracle Flashback Transaction Query
You can view changes made by a single transaction, or by all the transactions
during a specific time period. Oracle Database Development Guide explains how to
use this feature.

Oracle 閃回事務(wù)查詢
您可以查看單個(gè)事務(wù)或在特定時(shí)間段內(nèi)的所有事務(wù)所做的更改。 Oracle數(shù)據(jù)庫開發(fā)指南解釋了如何使用此功能对雪。

? Oracle Flashback Transaction
You can reverse a transaction. Oracle Database determines the dependencies
between transactions and in effect creates a compensating transaction that reverses the unwanted changes. The database rewinds to a state as if the transaction, and any transactions that could be dependent on it, had never happened. Oracle Database Development Guide explains how to use this feature.
您可以回退事務(wù)河狐。 Oracle數(shù)據(jù)庫確定事務(wù)之間的依賴關(guān)系，并且實(shí)際上創(chuàng)建了一個(gè)補(bǔ)償事務(wù)，以回退不需要的更改馋艺。 數(shù)據(jù)庫回退到一個(gè)狀態(tài)栅干，好像事務(wù)和可能依賴它的任何事務(wù)從未發(fā)生過。 Oracle數(shù)據(jù)庫開發(fā)指南解釋了如何使用此功能捐祠。

? Oracle Flashback Table
You can recover a table or set of tables to a specified point in time earlier without
taking any part of the database offline. In many cases, Flashback Table eliminates
the need to perform more complicated point-in-time recovery operations.
Flashback Table restores tables while automatically maintaining associated
attributes such as current indexes, triggers, and constraints, and in this way
enabling you to avoid finding and restoring database-specific properties.“Rewinding a Table with Flashback Table” explains how to use this feature.

您可以將表或表集合恢復(fù)到指定的時(shí)間點(diǎn)碱鳞，而不使數(shù)據(jù)庫的任何部分脫機(jī)。 在許多情況下雏赦，F(xiàn)lashback Table消除了執(zhí)行更復(fù)雜的時(shí)間點(diǎn)恢復(fù)操作的需要劫笙。 閃回表恢復(fù)表，同時(shí)自動(dòng)維護(hù)相關(guān)屬性（如當(dāng)前索引星岗，觸發(fā)器和約束）填大，從而使您能夠避免查找和恢復(fù)特定于數(shù)據(jù)庫的屬性。 “使用閃回表回滾表”說明如何使用此功能俏橘。

? Oracle Flashback Drop
You can reverse the effects of a DROP TABLE statement. “Rewinding a DROP
TABLE Operation with Flashback Drop” explains how to use this feature.
您可以回退DROP TABLE語句的效果允华。 “使用Flashback Drop重新執(zhí)行DROP TABLE操作”說明如何使用此功能。

A flashback data archive enables you to use some logical flashback features to access data from far back in the past. A flashback data archive consists of one or more tablespaces or parts of tablespaces. When you create a flashback data archive, you specify the name, retention period, and tablespace. You can also specify a default flashback data archive. The database automatically purges old historical data the day after the retention period expires.

閃回?cái)?shù)據(jù)存檔允許您使用一些邏輯閃回功能來訪問過去很久的數(shù)據(jù)寥掐。 閃回?cái)?shù)據(jù)存檔由一個(gè)或多個(gè)表空間或表空間的一部分組成靴寂。 創(chuàng)建閃回?cái)?shù)據(jù)存檔時(shí)，可以指定名稱召耘，保留期限和表空間百炬。 您還可以指定默認(rèn)閃回?cái)?shù)據(jù)歸檔。 數(shù)據(jù)庫在保留期過期后的第二天自動(dòng)清除舊的歷史數(shù)據(jù)污它。

You can turn flashback archiving on and off for individual tables. By default, flashback archiving is turned off for every table.

您可以為單個(gè)表打開和關(guān)閉閃回存檔剖踊。 默認(rèn)情況下，每個(gè)表都關(guān)閉閃回歸檔衫贬。

Flashback Database
At the physical level, Oracle Flashback Database provides a more efficient data protection alternative to database point-in-time recovery (DBPITR). If the current data files have unwanted changes, then you can use the RMAN command FLASHBACK DATABASE to revert the data files to their contents at a past time. The end product is much like the result of a DBPITR, but is generally much faster because it does not require restoring data files from backup and requires less redo than media recovery.

在物理級(jí)別德澈，Oracle閃回?cái)?shù)據(jù)庫為數(shù)據(jù)庫時(shí)間點(diǎn)恢復(fù)（DBPITR）提供了更高效的數(shù)據(jù)保護(hù)。 如果當(dāng)前數(shù)據(jù)文件有不需要的更改固惯，則可以使用RMAN命令FLASHBACK DATABASE將數(shù)據(jù)文件還原到其過去的內(nèi)容梆造。 最終產(chǎn)品非常類似于DBPITR的結(jié)果，但通常速度更快葬毫，因?yàn)樗恍枰獜膫浞莼謴?fù)數(shù)據(jù)文件镇辉，并且相比介質(zhì)恢復(fù)只需要少量的重做。

Flashback Database uses flashback logs to access past versions of data blocks and some information from archived redo logs. Flashback Database requires that you configure a fast recovery area for a database because the flashback logs can only be stored there. Flashback logging is not enabled by default. Space used for flashback logs is managed automatically by the database and balanced against space required for other files in the fast recovery area.

閃回?cái)?shù)據(jù)庫使用閃回日志訪問過去版本的數(shù)據(jù)塊和來自歸檔重做日志的一些信息供常。 閃回?cái)?shù)據(jù)庫要求您為數(shù)據(jù)庫配置快速恢復(fù)區(qū)域摊聋，因?yàn)殚W回日志只能存儲(chǔ)在那里。 默認(rèn)情況下未啟用閃回記錄栈暇。 用于閃回日志的空間由數(shù)據(jù)庫自動(dòng)管理，并與快速恢復(fù)區(qū)域中其他文件所需的空間進(jìn)行平衡箍镜。

Oracle Database also supports restore points along with Flashback Database and backup and recovery. A restore point is an alias corresponding to a system change number (SCN). You can create a restore point at any time if you anticipate needing to return part or all of a database to its contents at that time. A guaranteed restore point ensures that you can use Flashback Database to return a database to the time of the restore point.

Oracle數(shù)據(jù)庫還支持閃回?cái)?shù)據(jù)庫和恢復(fù)點(diǎn)的備份和恢復(fù)源祈。 恢復(fù)點(diǎn)是對應(yīng)于系統(tǒng)更改號(hào)（SCN）的別名煎源。 如果您預(yù)計(jì)需要將部分或全部數(shù)據(jù)庫返回到其內(nèi)容，則可以隨時(shí)創(chuàng)建恢復(fù)點(diǎn)香缺。 保證的還原點(diǎn)確保您可以使用Flashback Database將數(shù)據(jù)庫返回到還原點(diǎn)的時(shí)間手销。

About Data Recovery Advisor
Oracle Database includes a Data Recovery Advisor tool that automatically diagnoses persistent data failures, presents appropriate repair options, and executes repairs at your request. Data Recovery Advisor provides a single point of entry for Oracle backup and recovery solutions. You can use Data Recovery Advisor through Oracle Enterprise Manager or through the RMAN command-line client.

Oracle數(shù)據(jù)庫包含一個(gè)數(shù)據(jù)恢復(fù)顧問工具，可自動(dòng)診斷持久性數(shù)據(jù)故障图张，提供適當(dāng)?shù)男迯?fù)選項(xiàng)锋拖，并根據(jù)您的請求執(zhí)行修復(fù)。 數(shù)據(jù)恢復(fù)顧問為Oracle備份和恢復(fù)解決方案提供單一入口點(diǎn)祸轮。 您可以通過Oracle Enterprise Manager或通過RMAN命令行客戶端使用Data Recovery Advisor兽埃。

A database failure usually manifests itself as a set of symptoms: error messages, alerts, trace files and dumps, and failed data integrity checks. Data Recovery Advisor automatically diagnoses and informs you of these failures. For Data Recovery Advisor, a failure is a persistent data corruption that can be directly mapped to a set of repair actions. Each failure has a status of open or closed. Each failure also has a priority of critical, high, or low.

數(shù)據(jù)庫故障通常表現(xiàn)為一組癥狀：錯(cuò)誤消息，警報(bào)适袜，跟蹤文件和轉(zhuǎn)儲(chǔ)柄错，以及失敗的數(shù)
據(jù)完整性檢查。 數(shù)據(jù)恢復(fù)顧問自動(dòng)診斷并通知您這些故障苦酱。 對于數(shù)據(jù)恢復(fù)顧問，失敗是持久數(shù)據(jù)損壞，可以直接映射到一組修復(fù)操作乏梁。 每個(gè)故障具有打開或關(guān)閉的狀態(tài)缰冤。 每個(gè)故障還具有危險(xiǎn)，高或低的優(yōu)先級(jí)扯饶。

Failures are detected by data integrity checks, which are diagnostic procedures executed to assess the health of the database or its components. If a data integrity check reveals a failure, then Data Recovery Advisor automatically assesses the effect of a set of failures and maps it to a set of repair options. Usually, Data Recovery Advisor presents both automated and manual repair options.

通過數(shù)據(jù)完整性檢查來檢測故障恒削，這些檢查是為了評(píng)估數(shù)據(jù)庫或其組件的運(yùn)行狀況而執(zhí)行的診斷過程。 如果數(shù)據(jù)完整性檢查顯示失敗帝际，則數(shù)據(jù)恢復(fù)顧問會(huì)自動(dòng)評(píng)估一組故障的影響蔓同，并將其映射到一組修復(fù)選項(xiàng)。 通常蹲诀，數(shù)據(jù)恢復(fù)顧問提供自動(dòng)和手動(dòng)修復(fù)選項(xiàng)斑粱。

Data Recovery Advisor determines the best automated repair option and its effect on the database. The repair option may include repairs such as data file restore and recovery, media recovery, Flashback Database, and so on. Before presenting an automated repair option, Data Recovery Advisor validates it for the specific environment and the availability of media components required to complete the proposed repair.

數(shù)據(jù)恢復(fù)顧問確定最佳的自動(dòng)修復(fù)選項(xiàng)及其對數(shù)據(jù)庫的影響。 修復(fù)選項(xiàng)可以包括諸如數(shù)據(jù)文件恢復(fù)和恢復(fù)脯爪，介質(zhì)恢復(fù)则北，閃回?cái)?shù)據(jù)庫等的修復(fù)。 在提供自動(dòng)修復(fù)選項(xiàng)之前痕慢，數(shù)據(jù)恢復(fù)顧問會(huì)根據(jù)特定環(huán)境以及完成建議修復(fù)所需的介質(zhì)組件的可用性來進(jìn)行驗(yàn)證尚揣。

If you choose an automated repair option, then RMAN coordinates sessions on the Oracle Database to perform the repair for you. The Data Recovery Advisor tool verifies the repair success and closes the appropriate failures.

如果選擇自動(dòng)修復(fù)選項(xiàng)，則RMAN會(huì)在Oracle數(shù)據(jù)庫上協(xié)調(diào)會(huì)話以執(zhí)行修復(fù)掖举。 數(shù)據(jù)恢復(fù)顧問工具會(huì)驗(yàn)證修復(fù)成功并關(guān)閉相應(yīng)的故障快骗。