OCP-1Z0-053-V12.02-92题

 

92.You observed the following output for a user session:

What do you infer from the preceding output?

A. Resumable set for session with sid 18

B. The user session has entered into a deadlock

C. The database instance is enabled to use asynchronous commit

D. The threshold warning limit is exceeded for the tablespace that is used by the user session

Answer: A

答案解析：

官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/start.htm#ADMIN11165

sid=18的会话被暂停，等待错误被清除，清除后，会话恢复。

EVENT

VARCHAR2(64)

Resource or event for which the session is waiting See Also: Appendix C, "Oracle Wait Events"

Suspending and Resuming a Database

The ALTER SYSTEM SUSPEND statement halts all input and output (I/O) to data files (file header and file data) and control files. The suspended state lets you back up a database without I/O interference. When the database is suspended all preexisting I/O operations are allowed to complete and any new database accesses are placed in a queued state.

The suspend command is not specific to an instance. In an Oracle Real Application Clusters environment, when you issue the suspend command on one system, internal locking mechanisms propagate the halt request across instances, thereby quiescing all active instances in a given cluster. However, if a new instance is started while another instance is being suspended, then the new instance is not suspended.

Use the ALTER SYSTEM RESUME statement to resume normal database operations. The SUSPEND and RESUME commands can be issued from different instances. For example, if instances 1, 2, and 3 are running, and you issue an ALTER SYSTEM SUSPEND statement from instance 1, then you can issue a RESUME statement from instance 1, 2, or 3 with the same effect.

The suspend/resume feature is useful in systems that allow you to mirror a disk or file and then split the mirror, providing an alternative backup and restore solution. If you use a system that cannot split a mirrored disk from an existing database while writes are occurring, then you can use the suspend/resume feature to facilitate the split.

The suspend/resume feature is not a suitable substitute for normal shutdown operations, because copies of a suspended database can contain uncommitted updates.

Caution:

Do not use the ALTER SYSTEM SUSPEND statement as a substitute for placing a tablespace in hot backup mode. Precede any database suspend operation by an ALTER TABLESPACE BEGIN BACKUP statement.

The following statements illustrate ALTER SYSTEM SUSPEND/RESUME usage. The V$INSTANCE view is queried to confirm database status.

SQL> ALTER SYSTEM SUSPEND;

System altered

SQL> SELECT DATABASE_STATUS FROM V$INSTANCE;

DATABASE_STATUS

---------

SUSPENDED

 

SQL> ALTER SYSTEM RESUME;

System altered

SQL> SELECT DATABASE_STATUS FROM V$INSTANCE;

DATABASE_STATUS

---------

ACTIVE