多项选择题
A. The ASM-preferred mirror read feature is enabled.
B. The ASM supports variable sizes for extents of 1，8，and 64 allocation units.
C. The ASM disk is dropped immediately from a disk group when it becomes unavailable.
D. The RDBMS always reads the primary copy of a mirrored extent of the ASM disk group.
单项选择题 You are working on a 24X7 database. You want to design a backup strategy for your database that uses user managed backups. You want to be able to perform all backups while the database remains online. Which statement about performing user-managed backups in a 24x7 environment is true？（）
单项选择题 Examine the following RMAN script: RMAN> run { debug on; allocate channel c1 type disk; backup datafile 5; } Which statement describes the purpose of the script?（）
单项选择题 What does the DB_FLASHBACK_RETENTION_TARGET parameter configure?（）