個人自行閱讀時候，翻譯的文檔。因為比較渣，如果有更合理或者錯誤的地方煩勞告知，我會做修改。

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，Oracle Flashback技術(shù)補充了物理備份和恢復(fù)策略。 這組功能提供了一個額外的數(shù)據(jù)保護層。 具體來說，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)行時間點恢復(fù)。 一般來說，在大多數(shù)情況下，閃回功能比介質(zhì)恢復(fù)更高效，更少破壞性。

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
? 閃回數(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)閃回功能在邏輯級運行，使您能夠查看和操作數(shù)據(jù)庫對象。 Oracle的邏輯級閃回功能不依賴于RMAN，并且無論RMAN是否是備份策略的一部分，都是可用的。 除了Oracle Flashback Drop，邏輯閃回功能依賴于撤銷數(shù)據(jù)，記錄了每個數(shù)據(jù)庫更新所影響的記錄和在更新時重寫的數(shù)值。

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.

您可以指定目標時間并對數(shù)據(jù)庫運行查詢，查看在目標時間顯示的結(jié)果。 要從不需要的更改（如更新表）中恢復(fù)，可以選擇錯誤之前的目標時間，然后運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。

? 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.

您可以在指定的時間間隔中查看一個或多個表中存在的所有行的所有版本。 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)束時間，操作和事務(wù)ID。 您可以使用此功能恢復(fù)丟失的數(shù)據(jù)值，并審計對所查詢的表的更改。Oracle數(shù)據(jù)庫開發(fā)指南解釋了如何使用此功能。

? 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
您可以查看單個事務(wù)或在特定時間段內(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。

? 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)。 Oracle數(shù)據(jù)庫確定事務(wù)之間的依賴關(guān)系，并且實際上創(chuàng)建了一個補償事務(wù)，以回退不需要的更改。 數(shù)據(jù)庫回退到一個狀態(tài)，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。

? 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)到指定的時間點，而不使數(shù)據(jù)庫的任何部分脫機。 在許多情況下，F(xiàn)lashback Table消除了執(zhí)行更復(fù)雜的時間點恢復(fù)操作的需要。 閃回表恢復(fù)表，同時自動維護相關(guān)屬性（如當前索引，觸發(fā)器和約束），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。

? 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。 “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.

閃回數(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)。 閃回數(shù)據(jù)存檔由一個或多個表空間或表空間的一部分組成。 創(chuàng)建閃回數(shù)據(jù)存檔時，可以指定名稱，保留期限和表空間。 您還可以指定默認閃回數(shù)據(jù)歸檔。 數(shù)據(jù)庫在保留期過期后的第二天自動清除舊的歷史數(shù)據(jù)。

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

您可以為單個表打開和關(guān)閉閃回存檔。 默認情況下，每個表都關(guān)閉閃回歸檔。

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.

在物理級別，Oracle閃回數(shù)據(jù)庫為數(shù)據(jù)庫時間點恢復(fù)（DBPITR）提供了更高效的數(shù)據(jù)保護。 如果當前數(shù)據(jù)文件有不需要的更改，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。 最終產(chǎn)品非常類似于DBPITR的結(jié)果，但通常速度更快，因為它不需要從備份恢復(fù)數(shù)據(jù)文件，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.

閃回數(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。 閃回數(shù)據(jù)庫要求您為數(shù)據(jù)庫配置快速恢復(fù)區(qū)域，因為閃回日志只能存儲在那里。 默認情況下未啟用閃回記錄。 用于閃回日志的空間由數(shù)據(jù)庫自動管理，并與快速恢復(fù)區(qū)域中其他文件所需的空間進行平衡。

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)庫還支持閃回數(shù)據(jù)庫和恢復(fù)點的備份和恢復(fù)。 恢復(fù)點是對應(yīng)于系統(tǒng)更改號（SCN）的別名。 如果您預(yù)計需要將部分或全部數(shù)據(jù)庫返回到其內(nèi)容，則可以隨時創(chuàng)建恢復(fù)點。 保證的還原點確保您可以使用Flashback Database將數(shù)據(jù)庫返回到還原點的時間。

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)庫包含一個數(shù)據(jù)恢復(fù)顧問工具，可自動診斷持久性數(shù)據(jù)故障，提供適當?shù)男迯?fù)選項，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。 您可以通過Oracle Enterprise Manager或通過RMAN命令行客戶端使用Data Recovery Advisor。

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：錯誤消息，警報，跟蹤文件和轉(zhuǎn)儲，以及失敗的數(shù)
據(jù)完整性檢查。 數(shù)據(jù)恢復(fù)顧問自動診斷并通知您這些故障。 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。 每個故障具有打開或關(guān)閉的狀態(tài)。 每個故障還具有危險，高或低的優(yōu)先級。

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，這些檢查是為了評估數(shù)據(jù)庫或其組件的運行狀況而執(zhí)行的診斷過程。 如果數(shù)據(jù)完整性檢查顯示失敗，則數(shù)據(jù)恢復(fù)顧問會自動評估一組故障的影響，并將其映射到一組修復(fù)選項。 通常，數(shù)據(jù)恢復(fù)顧問提供自動和手動修復(fù)選項。

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修復(fù)選項及其對數(shù)據(jù)庫的影響。 修復(fù)選項可以包括諸如數(shù)據(jù)文件恢復(fù)和恢復(fù)，介質(zhì)恢復(fù)，閃回數(shù)據(jù)庫等的修復(fù)。 在提供自動修復(fù)選項之前，數(shù)據(jù)恢復(fù)顧問會根據(jù)特定環(huán)境以及完成建議修復(fù)所需的介質(zhì)組件的可用性來進行驗證。

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.

如果選擇自動修復(fù)選項，則RMAN會在Oracle數(shù)據(jù)庫上協(xié)調(diào)會話以執(zhí)行修復(fù)。 數(shù)據(jù)恢復(fù)顧問工具會驗證修復(fù)成功并關(guān)閉相應(yīng)的故障。