12C-OCP升级1z-060-020

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You are administering a database stored in Automatic Storage management (ASM). The
files are stored in the DATA disk group. You execute the following command:
SQL > ALTER DISKGROUP data ADD ALIAS ‘+data/prod/myfile.dbf’ FOR ‘+data/prod/myfile.dbf’
What is the result?

A. The file ‘+data.231.54769’ is physically relocated to ‘+data/prod’ and renamed as ‘myfile.dbf’.
B. The file ‘+data.231.54769’ is renamed as ‘myfile.dbf’, and copied to ‘+data/prod’.
C. The file ‘+data.231.54769’ remains in the same location and a synonym 'myfile.dbf' is created.
D. The file ‘myfile.dbf’ is created in ‘+data/prod’ and the reference to ‘+data.231.54769’ in the data dictionary removed.

Answer: C

答案解析
Use this clause to create an alias name for an Oracle ASM filename. The alias_name
consists of the full directory path and the alias itself.
别名就是外号，比如说当系统自动产生的名称太过复杂不怎么好记，DBA可以通过别名，为它创建一个简单化的名称，而又不会对其现有名称造成任何影响。ASM中创建别名是通过alter diskgroup的alias子句实现，支持增加/修改/删除等多项操作。V$ASM_ALIAS视图中可以查询到当前实例中创建的别名。
例如，增加别名：

09:10:23 sys@kiwi> select name from v$datafile;NAME----------------------------------------------------------------------------------------------------------------------------------+DATA/KIWI/DATAFILE/system.258.906850731+DATA/KIWI/DATAFILE/test.268.906861531+DATA/KIWI/DATAFILE/sysaux.257.906850669+DATA/KIWI/DATAFILE/undotbs1.260.906850807+DATA/KIWI/DATAFILE/example.266.906850863+DATA/KIWI/DATAFILE/users.259.90685080709:10:45 idle> alter diskgroup data add alias '+DATA/KIWI/DATAFILE/test.dbf' for '+DATA/KIWI/DATAFILE/test.268.906861531';ASMCMD> ls -lType      Redund  Striped  Time             Sys  NameDATAFILE  UNPROT  COARSE   MAR 29 03:00:00  Y    EXAMPLE.266.906850863DATAFILE  UNPROT  COARSE   MAR 29 03:00:00  Y    SYSAUX.257.906850669DATAFILE  UNPROT  COARSE   MAR 29 03:00:00  Y    SYSTEM.258.906850731DATAFILE  UNPROT  COARSE   MAR 29 03:00:00  Y    TEST.268.906861531DATAFILE  UNPROT  COARSE   MAR 29 03:00:00  Y    UNDOTBS1.260.906850807DATAFILE  UNPROT  COARSE   MAR 29 03:00:00  Y    USERS.259.906850807DATAFILE  UNPROT  COARSE   MAR 29 03:00:00  N    test.dbf => +DATA/KIWI/DATAFILE/TEST.268.906861531

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