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正确答案DB
这道题目没什么深入的原理，我们从答案入一一分析。
答案A不正确，多路复用可以备份在磁带和磁盘，根据经验答案不能确定是对是错的看到这种还有“only”只有唯一的单词，一般是错的。
答案B正确，镜像拷贝不支持多路径复用，实验加以验证，看下面实验：
RMAN> copy datafile 10 to \'/backup/disk1/df10_1\',\'/backup/disk1/df10_2\'; RMAN-00571: =========================================================== RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS =============== RMAN-00571: =========================================================== RMAN-00558: error encountered while parsing input commands RMAN-01009: syntax error: found "single-quoted-string": expecting one of: "archivelog, backup, controlfilecopy, current, datafilecopy, datafile" RMAN-01007: at line 1 column 44 file: standard input RMAN> copy datafile 10 to \'/backup/disk1/df10_1\'; Starting backup at 16-OCT-13 using channel ORA_DISK_1 channel ORA_DISK_1: starting datafile copy input datafile file number=00010 name=/u01/app/oracle/oradata/ocm/tp2.dbf output file name=/backup/disk1/df10_1 tag=TAG20131016T001904 RECID=5 STAMP=828922746 channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03 Finished backup at 16-OCT-13 Starting Control File and SPFILE Autobackup at 16-OCT-13 piece handle=/backup/rman/c-2206937749-20131016-01 comment=NONE Finished Control File and SPFILE Autobackup at 16-OCT-13
答案C不正确，并行度与镜像拷数无关，实验加以验证，看下面实验：
RMAN> show all; RMAN configuration parameters for database with db_unique_name OCM are: CONFIGURE RETENTION POLICY TO REDUNDANCY 2; CONFIGURE BACKUP OPTIMIZATION ON; CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default CONFIGURE CONTROLFILE AUTOBACKUP ON; CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO \'/backup/rman/%F\'; CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT \'%U\'; CONFIGURE MAXSETSIZE TO UNLIMITED; # default CONFIGURE ENCRYPTION FOR DATABASE OFF; # default CONFIGURE ENCRYPTION ALGORITHM \'AES128\'; # default CONFIGURE COMPRESSION ALGORITHM \'BASIC\' AS OF RELEASE \'DEFAULT\' OPTIMIZE FOR LOAD TRUE ; # default CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default CONFIGURE SNAPSHOT CONTROLFILE NAME TO \'/u01/app/oracle/product/11.2.0/dbs/snapcf_ocm.f\'; # default RMAN> CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 2; old RMAN configuration parameters: CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; new RMAN configuration parameters: CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 2; new RMAN configuration parameters are successfully stored
CONFIGUREDEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET;--并行度是1也没关系
CONFIGUREDATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 2;--备份集多路径
对10文件多路径备份，这里我们的并行度为1，备份集多径路2，此时并行度与多径路不一样，也可以备份。
RMAN> report schema; Report of database schema for database with db_unique_name OCM List of Permanent Datafiles =========================== File Size(MB) Tablespace RB segs Datafile Name ---- -------- -------------------- ------- ------------------------ 1 730 SYSTEM *** /u01/app/oracle/oradata/ocm/system01.dbf 2 710 SYSAUX *** /u01/app/oracle/oradata/ocm/sysaux01.dbf 3 110 UNDOTBS1 *** /u01/app/oracle/oradata/ocm/undotbs01.dbf 4 5 USERS *** /u01/app/oracle/oradata/ocm/users01.dbf 5 345 EXAMPLE *** /u01/app/oracle/oradata/ocm/example01.dbf 6 100 GYJ *** /u01/app/oracle/oradata/ocm/gyj01.dbf 7 50 GYJ *** /u01/app/oracle/oradata/ocm/gyj02.dbf 8 10 TP1 *** /u01/app/oracle/oradata/ocm/tp01.dbf 9 10 MRKT *** /u01/app/oracle/oradata/ocm/mrkt01.dbf 10 100 TP2 *** /u01/app/oracle/oradata/ocm/tp2.dbf List of Temporary Files ======================= File Size(MB) Tablespace Maxsize(MB) Tempfile Name ---- -------- -------------------- ----------- -------------------- 1 20 TEMP 32767 /u01/app/oracle/oradata/ocm/temp01.dbf 2 10 TEMP1 10 /u01/app/oracle/oradata/ocm/temp02.dbf 3 10 TEMP4 10 /u01/app/oracle/oradata/ocm/temp04.dbf RMAN> backup datafile 10 format \'/backup/disk1/%U\',\'/backup/disk2/%U\'; Starting backup at 16-OCT-13 using channel ORA_DISK_1 channel ORA_DISK_1: starting full datafile backup set channel ORA_DISK_1: specifying datafile(s) in backup set input datafile file number=00010 name=/u01/app/oracle/oradata/ocm/tp2.dbf channel ORA_DISK_1: starting piece 1 at 16-OCT-13 channel ORA_DISK_1: finished piece 1 at 16-OCT-13 with 2 copies and tag TAG20131016T001426 piece handle=/backup/disk1/1gomgmj2_1_1 comment=NONE piece handle=/backup/disk2/1gomgmj2_1_2 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01 Finished backup at 16-OCT-13 Starting Control File and SPFILE Autobackup at 16-OCT-13 piece handle=/backup/rman/c-2206937749-20131016-00 comment=NONE Finished Control File and SPFILE Autobackup at 16-OCT-13
答案D正确，多路复制可以备份在磁盘或着磁带上，但是不能同时备份在磁盘和着磁带上。
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