多选题Which two requirements are critically important to implement for your database backup strategy if you require a 24 hours a day， 7 days a week production environment？（）AARCHIVELOG mode.BNOARCHIVELOG mode.COpen database backups.DConsistent whole backups.

正确答案：CE
解析：Explanation:
C: Most OLTP backup schemes include a full database, differential, and transaction log backups

E: In order to recover the data as quickly as possibly we backup the data to network share, and then backup that share to tape. This minimizes the impact of the backup process on the SQL Server computer.

Note 1: SQL Server 2000 provides three database recovery models. These are the Simple recovery model, the Full Recovery Model and the Bulk-Logged Recovery model. Simple Recovery requires the least administration. In the Simple Recovery model, data is recoverable only to the last full database or differential backup. Transaction log backups are not used, and consequently, minimal transaction log space is required.

This Recovery Model is not an appropriate choice for production systems where loss of recent changes is unacceptable. Full Recovery and Bulk-Logged Recovery models provide the greatest protection for data. These models rely on the transaction log to provide full recoverability and to prevent work loss in the broadest range of failure scenarios.

The Full Recovery model provides the most flexibility for recovering databases to an earlier point in time. The Bulk-Logged model provides higher performance and lower log space consumption for certain large-scale operations. It does this at the expense of some flexibility of pointin- time recovery. In this scenario we would want to implement the Full Recovery model as this Recovery model provides complete protection against media failure and provides the ability to recover the database to the point of failure or to a specific point in time.

To guarantee this degree of recoverability, all operations are fully logged. The backup strategy for full recovery consists of database backups, differential backups, which are optional, and transaction log backups. The differential backups are optional but have less of an effect on the system while they run, as they are smaller than full database backups.

This is because a differential backup creates a copy of all the pages in a database modified after the last database backup. A transaction log backup makes a copy only of the log file and backs up the changes made to the database after the last full or differential database backup. A log file backup cannot be used by itself to restore a database. A log file is used after a database restore to recover the database to the point of the original failure. The full database, differential, and transaction log backups can be written to a hard disk or other disk storage media such as a tape drive.

Disk backup devices can be defined on a local disk of a server or on a remote disk on a shared network resource. Tape backup devices are used in the same way as disk devices, with the exception that the tape device must be connected physically to the computer running an instance of SQL Server. SQL Server 2000 thus does not support backing up to remote tape devices.

Note 2, file backup, filegroup backup: SQL Server 2000 supports backing up or restoring individual files or filegroups within a database. This is a complex backup and the restore process that is usually reserved for large databases with high availability requirements. If the time available for backups is not long enough to support backing up the full database, subsets of the database can be backed up at different times. If a disk holding database files or filegroups fails, the site can restore just the lost files or filegroups. This allows for a quicker recovery because only the damaged files or filegroups are restored in the first step, not the entire database.

Incorrect Answers:
A: An OLTP server requires transaction log backups in order to be able to recover up to the point of failure.

B: An OLTP server requires transaction log backups in order to be able to recover up to the point of failure.

D: Backing up to a local tape device would minimize cost but it would compared to a backup to a network it would decrease performance of the server more, and it would take more time to recover.

参考答案：C, D

参考答案：B, C