【云贝教育】Oracle 19c OCP 083题库解析(18)

考试科目：1Z0-083

考试题量：85

通过分数：57%

考试时间：150min

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18、Which two are true about creating pluggable databases(PDBS)in Oracle 19c and later releases?

A) A PDB snapshot depends on an existing storage snapshot of the source PDB

B) A PDB snapshot can be a full copy of a source PDB

C) A PDB snapshot can be a sparse copy of a source PDB

D) A snapshot copy PDB does not depend on an existing storage snapshot of the source PDB

E) A snapshot copy PDB can be a full copy of a source PDB

参考答案: BC

解析：

在Oracle 19c及以后的版本中创建可插拔数据库(PDBS)，哪两个是正确的?

Oracle利用快照将PDB数据闪回恢复到快照时间点
它可以使用手动或者自动的方式创建连续副本。当达到快照限制时（8个），数据库将覆盖旧的快照。
PDB快照是PDB在某个时间点的副本。创建快照时，源PDB可以是打开的只读状态或读写状态。
您可以使用create PLUGGABLE DATABASE(或ALTER PLUGGABLE DATABASE)的SNAPSHOT子句手动创建快照，
也可以使用EVERY interval子句自动创建快照。如果存储系统支持稀疏克隆，则使用该命令创建稀疏副本。否则，该命令将创建完整副本。

PDB快照的文件存放在文件系统上的物理文件上，但是快照的内容是取决于底层文件系统是否支持稀疏文件，稀疏文件以.dbf作为后缀，而完整的PDB快照是以.pdb作为后缀。

A) 错，PDB快照依赖于源PDB已有的存储快照
B) 对，PDB快照可以是源PDB的完整副本
C) 对， PDB快照可以是源PDB的稀疏副本
D) 错，快照副本PDB不依赖于源PDB已有的存储快照   （#快照副本PDB源于snapshop快照）
E) 错，快照副本PDB可以是源PDB的完整副本             （#快照副本PDB源于snapshop快照）


https://docs.oracle.com/en/database/oracle/oracle-database/19/multi/administering-pdb-snapshots.html#GUID-72CA6DD5-4DE5-4375-BEA6-A01E5E31A01B

A PDB snapshot is a point-in-time copy of a PDB. The source PDB can be open read-only or read/write while the snapshot is created.
You can create snapshots manually using the SNAPSHOT clause of CREATE PLUGGABLE DATABASE (or ALTER PLUGGABLE DATABASE),
or automatically using the EVERY interval clause. If the storage system supports sparse clones,
then the preceding command creates a sparse copy. Otherwise, the command creates a full copy.


The following steps illustrate a typical development scenario:

1.While the production PDB named pdb1_prod is open and in use, create a refreshable clone PDB named pdb1_test_master.
A refreshable clone PDB can only be opened in read/only mode. To refresh the clone PDB from pdb1_prod, you must close it.

2.Run ALTER PLUGGABLE DATABASE pdb1_test_master SNAPSHOT MODE EVERY 24 HOURS, which configures the PDB to generate automatic snapshots of pdb1_test_master every day.
When you need new PDBs for testing, create a full clone PDB by using the CREATE PLUGGABLE DATABASE … USING SNAPSHOT command.

3.Create sparse snapshot copy PDBs of the full clone PDB using CREATE PLUGGABLE DATABASE ... SNAPSHOT COPY.

4.The following figure shows the creation of the clone pdb1_test_full1 from the PDB snapshot taken on April 5. The figure shows three snapshot copy PDBs created from pdb1_test_full1.

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