感謝大臉貓的實驗分析結果。

下面以實驗的方式，展示在RUN塊中手工指定多通道（CHANNEL，也有稱之為“通道”） 與設定並行度PARALLELISM引數 的異同，以及FILESPERSET引數的作用。
RMAN備份時，為了加快備份的速度，提供了並行處理的方式。一種是設定多個通道，另一種是設定PARALLELISM引數。那麼這兩種方式有什麼不同呢？今天在實驗的方式來加深理解。 首先，我們來實驗第一種方式，即設定多個通道的方式。為了比較增加通道後的效果，我們先做一次單通道的備份操作。 [[email protected] ~]$ rman target / Recovery Manager: Release 10.2.0.5.0 - Production on Sat Jan 25 15:22:13 2014 Copyright (c) 1982, 2007, Oracle. All rights reserved. connected to target database: ORCL (DBID=1347935162) RMAN> run { allocate channel c1 device type disk format '/oradata/orcl/databak1/%U'; backup database; release channel c1; }2> 3> 4> 5> using target database control file instead of recovery catalog allocated channel: c1 channel c1: sid=158 devtype=DISK Starting backup at 20140125 15:27:37 channel c1: starting full datafile backupset channel c1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel c1: starting piece 1 at 20140125 15:27:38 channel c1: finished piece 1 at 20140125 15:28:23 piece handle=/oradata/orcl/databak1/8iouvaba_1_1 tag=TAG20140125T152737 comment=NONE channel c1: backup set complete, elapsed time: 00:00:45 Finished backup at 20140125 15:28:23 Starting Control File and SPFILE Autobackup at 20140125 15:28:23 piece handle=/oradata/orcl/databak/c-1347935162-20140125-08 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 15:28:26 released channel: c1 可見，資料庫的備份時間約為49秒（15:27:37至15:28:26）。 下面我們設定2個通道，來執行備份。 RMAN> run { allocate channel c1 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c2 device type disk format '/oradata/orcl/databak1/%U'; backup database; release channel c1; release channel c2; }2> 3> 4> 5> 6> 7> allocated channel: c1 channel c1: sid=158 devtype=DISK allocated channel: c2 channel c2: sid=147 devtype=DISK Starting backup at 20140125 15:31:45 channel c1: starting full datafile backupset channel c1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf channel c1: starting piece 1 at 20140125 15:31:45 channel c2: starting full datafile backupset channel c2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel c2: starting piece 1 at 20140125 15:31:45 channel c2: finished piece 1 at 20140125 15:32:00 piece handle=/oradata/orcl/databak1/8louvaj1_1_1 tag=TAG20140125T153145 comment=NONE channel c2: backup set complete, elapsed time: 00:00:15 channel c1: finished piece 1 at 20140125 15:32:35 piece handle=/oradata/orcl/databak1/8kouvaj1_1_1 tag=TAG20140125T153145 comment=NONE channel c1: backup set complete, elapsed time: 00:00:50 Finished backup at 20140125 15:32:35 Starting Control File and SPFILE Autobackup at 20140125 15:32:35 piece handle=/oradata/orcl/databak/c-1347935162-20140125-09 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 15:32:38 released channel: c1 released channel: c2 2個通道的情況下，備份時間約為53秒（15:31:45至15:32:38）。時間上還要慢了一些。 而且，我們發現，組成資料庫的資料檔案一共有6個，當用2個通道備份時，其自動分成了兩組，每組3個檔案。 備份結束後，每個通道生成一個備份檔案，共兩個備份檔案。 我們再試試3個通道時的情況 RMAN> run { allocate channel c1 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c2 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c3 device type disk format '/oradata/orcl/databak1/%U'; backup database; release channel c1; release channel c2; release channel c3; }2> 3> 4> 5> 6> 7> 8> 9> allocated channel: c1 channel c1: sid=158 devtype=DISK allocated channel: c2 channel c2: sid=147 devtype=DISK allocated channel: c3 channel c3: sid=138 devtype=DISK Starting backup at 20140125 15:39:06 channel c1: starting full datafile backupset channel c1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel c1: starting piece 1 at 20140125 15:39:07 channel c2: starting full datafile backupset channel c2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel c2: starting piece 1 at 20140125 15:39:07 channel c3: starting full datafile backupset channel c3: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf channel c3: starting piece 1 at 20140125 15:39:07 channel c2: finished piece 1 at 20140125 15:39:14 piece handle=/oradata/orcl/databak1/8oouvb0r_1_1 tag=TAG20140125T153906 comment=NONE channel c2: backup set complete, elapsed time: 00:00:07 channel c1: finished piece 1 at 20140125 15:39:59 piece handle=/oradata/orcl/databak1/8nouvb0r_1_1 tag=TAG20140125T153906 comment=NONE channel c1: backup set complete, elapsed time: 00:00:52 channel c3: finished piece 1 at 20140125 15:39:59 piece handle=/oradata/orcl/databak1/8pouvb0r_1_1 tag=TAG20140125T153906 comment=NONE channel c3: backup set complete, elapsed time: 00:00:52 Finished backup at 20140125 15:39:59 Starting Control File and SPFILE Autobackup at 20140125 15:39:59 piece handle=/oradata/orcl/databak/c-1347935162-20140125-0a comment=NONE Finished Control File and SPFILE Autobackup at 20140125 15:40:02 released channel: c1 released channel: c2 released channel: c3 3個通道的情況下，備份時間約為56秒（15:39:06至15:40:02） 而且，6個數據檔案也被分成了三組，每組2個檔案。那麼如果我設成4個通道，6個檔案會如何分組呢？ RMAN> run { allocate channel c1 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c2 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c3 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c4 device type disk format '/oradata/orcl/databak1/%U'; backup database; release channel c1; release channel c2; release channel c3; release channel c4; } 2> 3> 4> 5> 6> 7> 8> 9> 10> 11> allocated channel: c1 channel c1: sid=158 devtype=DISK allocated channel: c2 channel c2: sid=147 devtype=DISK allocated channel: c3 channel c3: sid=138 devtype=DISK allocated channel: c4 channel c4: sid=137 devtype=DISK Starting backup at 20140125 15:42:49 channel c1: starting full datafile backupset channel c1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel c1: starting piece 1 at 20140125 15:42:49 channel c2: starting full datafile backupset channel c2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel c2: starting piece 1 at 20140125 15:42:49 channel c3: starting full datafile backupset channel c3: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf channel c3: starting piece 1 at 20140125 15:42:49 channel c2: finished piece 1 at 20140125 15:43:04 piece handle=/oradata/orcl/databak1/8souvb7p_1_1 tag=TAG20140125T154249 comment=NONE channel c2: backup set complete, elapsed time: 00:00:15 channel c3: finished piece 1 at 20140125 15:43:39 piece handle=/oradata/orcl/databak1/8touvb7p_1_1 tag=TAG20140125T154249 comment=NONE channel c3: backup set complete, elapsed time: 00:00:50 channel c1: finished piece 1 at 20140125 15:43:46 piece handle=/oradata/orcl/databak1/8rouvb7p_1_1 tag=TAG20140125T154249 comment=NONE channel c1: backup set complete, elapsed time: 00:00:57 Finished backup at 20140125 15:43:46 Starting Control File and SPFILE Autobackup at 20140125 15:43:46 piece handle=/oradata/orcl/databak/c-1347935162-20140125-0b comment=NONE Finished Control File and SPFILE Autobackup at 20140125 15:43:47 released channel: c1 released channel: c2 released channel: c3 released channel: c4 分配了4個通道，但備份過程中，只實際使用了3個。備份的時間為58秒（15:42:49至15:43:47 ）。
到了這裡，看來RMAN是在各個通道間平均分配檔案數量的。推測一下，如果設成6個通道，應該就是一個檔案一個通道了。 RMAN> run { allocate channel c1 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c2 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c3 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c4 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c5 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c6 device type disk format '/oradata/orcl/databak1/%U'; backup database; release channel c1; release channel c2; release channel c3; release channel c4; release channel c5; release channel c6; }2> 3> 4> 5> 6> 7> 8> 9> 10> 11> 12> 13> 14> 15> 16> allocated channel: c1 channel c1: sid=158 devtype=DISK allocated channel: c2 channel c2: sid=147 devtype=DISK allocated channel: c3 channel c3: sid=138 devtype=DISK allocated channel: c4 channel c4: sid=137 devtype=DISK allocated channel: c5 channel c5: sid=156 devtype=DISK allocated channel: c6 channel c6: sid=155 devtype=DISK Starting backup at 20140125 15:57:58 channel c1: starting full datafile backupset channel c1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf channel c1: starting piece 1 at 20140125 15:57:58 channel c2: starting full datafile backupset channel c2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf channel c2: starting piece 1 at 20140125 15:57:58 channel c3: starting full datafile backupset channel c3: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf channel c3: starting piece 1 at 20140125 15:57:58 channel c4: starting full datafile backupset channel c4: specifying datafile(s) in backupset input datafile fno=00004 name=/oradata/orcl/users01.dbf channel c4: starting piece 1 at 20140125 15:57:58 channel c5: starting full datafile backupset channel c5: specifying datafile(s) in backupset input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel c5: starting piece 1 at 20140125 15:57:58 channel c6: starting full datafile backupset channel c6: specifying datafile(s) in backupset input datafile fno=00007 name=/oradata/orcl/system02.dbf channel c6: starting piece 1 at 20140125 15:57:58 channel c5: finished piece 1 at 20140125 15:58:01 piece handle=/oradata/orcl/databak1/93ouvc46_1_1 tag=TAG20140125T155758 comment=NONE channel c5: backup set complete, elapsed time: 00:00:03 channel c2: finished piece 1 at 20140125 15:58:08 piece handle=/oradata/orcl/databak1/90ouvc46_1_1 tag=TAG20140125T155758 comment=NONE channel c2: backup set complete, elapsed time: 00:00:10 channel c6: finished piece 1 at 20140125 15:58:08 piece handle=/oradata/orcl/databak1/94ouvc46_1_1 tag=TAG20140125T155758 comment=NONE channel c6: backup set complete, elapsed time: 00:00:10 channel c4: finished piece 1 at 20140125 15:58:11 piece handle=/oradata/orcl/databak1/92ouvc46_1_1 tag=TAG20140125T155758 comment=NONE channel c4: backup set complete, elapsed time: 00:00:13 channel c3: finished piece 1 at 20140125 15:58:36 piece handle=/oradata/orcl/databak1/91ouvc46_1_1 tag=TAG20140125T155758 comment=NONE channel c3: backup set complete, elapsed time: 00:00:39 channel c1: finished piece 1 at 20140125 15:58:52 piece handle=/oradata/orcl/databak1/8vouvc46_1_1 tag=TAG20140125T155758 comment=NONE channel c1: backup set complete, elapsed time: 00:00:54 Finished backup at 20140125 15:58:52 Starting Control File and SPFILE Autobackup at 20140125 15:58:52 piece handle=/oradata/orcl/databak/c-1347935162-20140125-0c comment=NONE Finished Control File and SPFILE Autobackup at 20140125 15:58:55 released channel: c1 released channel: c2 released channel: c3 released channel: c4 released channel: c5 released channel: c6 果然，如推測中的一樣。是一個通道一個檔案，最終生成了6個備份檔案。總用時約57秒（15:57:58至 15:58:55） 經過以上實驗，得出以下結論： 1、增加通道，RMAN會並行處理備份任務，但根據硬體環境的不同，並不是越多越快。以本次實驗來說，備份時間最省的，卻是隻有一個通道的時候。這可能是因為實驗環境為一跑在普通桌上型電腦上的虛擬機器所致，其本身的並行處理能力就低。 2、當設有多個通道時，資料檔案會平均分配至各個通道上。若檔案不能全部均分至所有通道上，則會放棄部分通道的使用。例如上面實驗中的6個數據檔案在4個通道上備份時，則實際上只使用了3個通道。可是，假如組成資料庫的資料檔案的個數是質數（只能被它自己和1整除的數），比如7個檔案。當設定為4個通道時，會如何分配呢？由於無論是用4個，還是3個或2個通道，我們都不能把資料檔案均分到通道上。這裡先賣個關子，為了保證我們下面的實驗可以在相同的環境下完成，這個實驗，我們放到最後。 3、自動備份的控制檔案和引數檔案並沒有備份到通道指定的位置（/oradata/orcl/databak1），而放存放到了RMAN中配置的“控制檔案自動備份”所指定的位置（見下面紅字部分）。 RMAN> show all; RMAN configuration parameters are: CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default CONFIGURE BACKUP OPTIMIZATION OFF; CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default CONFIGURE CONTROLFILE AUTOBACKUP ON; CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/oradata/orcl/databak/%F'; CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT '/oradata/orcl/databak/%U'; CONFIGURE MAXSETSIZE TO UNLIMITED; # default CONFIGURE ENCRYPTION FOR DATABASE OFF; # default CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/oracle/app/oracle/product/10.2/db_1/dbs/snapcf_orcl.f'; # default 現在再來看並行度PARALLELISM這個引數。這個引數要通過輸入以下命令來設定（這裡設定的並行度為3）： RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 3 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters: CONFIGURE DEVICE TYPE DISK PARALLELISM 3 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters are successfully stored 我們再執行一個通道的備份，看看是什麼效果。 RMAN> run { allocate channel c1 device type disk format '/oradata/orcl/databak1/%U'; backup database; release channel c1; }2> 3> 4> 5> allocated channel: c1 channel c1: sid=158 devtype=DISK Starting backup at 20140125 16:20:32 channel c1: starting full datafile backupset channel c1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel c1: starting piece 1 at 20140125 16:20:32 channel c1: finished piece 1 at 20140125 16:21:17 piece handle=/oradata/orcl/databak1/9bouvdeg_1_1 tag=TAG20140125T162032 comment=NONE channel c1: backup set complete, elapsed time: 00:00:45 Finished backup at 20140125 16:21:17 Starting Control File and SPFILE Autobackup at 20140125 16:21:17 piece handle=/oradata/orcl/databak/c-1347935162-20140125-0f comment=NONE Finished Control File and SPFILE Autobackup at 20140125 16:21:18 released channel: c1 嘿嘿，在RUN塊中指定通道時，這個引數是不管用的。也就是說，你在RUN塊內指定了幾個通道，就用幾個通道去備份，與這個PARALLELISM這個引數無關。 那我們直接在RMAN中輸入BACKUP DATABASE；會是什麼效果呢？ RMAN> backup database; Starting backup at 20140125 16:24:41 allocated channel: ORA_DISK_1 channel ORA_DISK_1: sid=158 devtype=DISK allocated channel: ORA_DISK_2 channel ORA_DISK_2: sid=147 devtype=DISK allocated channel: ORA_DISK_3 channel ORA_DISK_3: sid=138 devtype=DISK channel ORA_DISK_1: starting full datafile backupset channel ORA_DISK_1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel ORA_DISK_1: starting piece 1 at 20140125 16:24:42 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 16:24:42 channel ORA_DISK_3: starting full datafile backupset channel ORA_DISK_3: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf channel ORA_DISK_3: starting piece 1 at 20140125 16:24:42 channel ORA_DISK_2: finished piece 1 at 20140125 16:24:49 piece handle=/oradata/orcl/databak/9eouvdma_1_1 tag=TAG20140125T162441 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:07 channel ORA_DISK_1: finished piece 1 at 20140125 16:25:24 piece handle=/oradata/orcl/databak/9douvdma_1_1 tag=TAG20140125T162441 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:42 channel ORA_DISK_3: finished piece 1 at 20140125 16:25:24 piece handle=/oradata/orcl/databak/9fouvdma_1_1 tag=TAG20140125T162441 comment=NONE channel ORA_DISK_3: backup set complete, elapsed time: 00:00:42 Finished backup at 20140125 16:25:24 Starting Control File and SPFILE Autobackup at 20140125 16:25:24 piece handle=/oradata/orcl/databak/c-1347935162-20140125-10 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 16:25:27 RMAN自動建立了三個通道，ORA_DISK_1至3。備份時間為46秒（16:24:41至16:25:27）。這個時間要比我們手工指定三個通道（56秒）時快。 再設定並行度為4看看效果。 RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET; old RMAN configuration parameters: CONFIGURE DEVICE TYPE DISK PARALLELISM 3 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters: CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters are successfully stored released channel: ORA_DISK_1 released channel: ORA_DISK_2 released channel: ORA_DISK_3 RMAN> backup database; Starting backup at 20140125 16:26:38 allocated channel: ORA_DISK_1 channel ORA_DISK_1: sid=158 devtype=DISK allocated channel: ORA_DISK_2 channel ORA_DISK_2: sid=147 devtype=DISK allocated channel: ORA_DISK_3 channel ORA_DISK_3: sid=138 devtype=DISK allocated channel: ORA_DISK_4 channel ORA_DISK_4: sid=137 devtype=DISK channel ORA_DISK_1: starting full datafile backupset channel ORA_DISK_1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel ORA_DISK_1: starting piece 1 at 20140125 16:26:38 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 16:26:38 channel ORA_DISK_3: starting full datafile backupset channel ORA_DISK_3: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf channel ORA_DISK_3: starting piece 1 at 20140125 16:26:39 channel ORA_DISK_2: finished piece 1 at 20140125 16:26:54 piece handle=/oradata/orcl/databak/9iouvdpu_1_1 tag=TAG20140125T162638 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:16 channel ORA_DISK_1: finished piece 1 at 20140125 16:27:29 piece handle=/oradata/orcl/databak/9houvdpu_1_1 tag=TAG20140125T162638 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:51 channel ORA_DISK_3: finished piece 1 at 20140125 16:27:29 piece handle=/oradata/orcl/databak/9jouvdpu_1_1 tag=TAG20140125T162638 comment=NONE channel ORA_DISK_3: backup set complete, elapsed time: 00:00:51 Finished backup at 20140125 16:27:29 Starting Control File and SPFILE Autobackup at 20140125 16:27:29 piece handle=/oradata/orcl/databak/c-1347935162-20140125-11 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 16:27:32 和我們手工指定4個通道時類似，備份時只實際使用了3個通道。備份的時間為54秒（16:26:38至16:27:32），和上面手工指定4個通道所用時間來比，稍快一點兒。但比剛才自動3通道的要慢。 再設定並行度為7看看效果。 RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 7 BACKUP TYPE TO BACKUPSET; old RMAN configuration parameters: CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters: CONFIGURE DEVICE TYPE DISK PARALLELISM 7 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters are successfully stored released channel: ORA_DISK_1 released channel: ORA_DISK_2 released channel: ORA_DISK_3 released channel: ORA_DISK_4 RMAN> backup database; Starting backup at 20140125 16:29:00 allocated channel: ORA_DISK_1 channel ORA_DISK_1: sid=158 devtype=DISK allocated channel: ORA_DISK_2 channel ORA_DISK_2: sid=147 devtype=DISK allocated channel: ORA_DISK_3 channel ORA_DISK_3: sid=138 devtype=DISK allocated channel: ORA_DISK_4 channel ORA_DISK_4: sid=137 devtype=DISK allocated channel: ORA_DISK_5 channel ORA_DISK_5: sid=156 devtype=DISK allocated channel: ORA_DISK_6 channel ORA_DISK_6: sid=155 devtype=DISK allocated channel: ORA_DISK_7 channel ORA_DISK_7: sid=134 devtype=DISK channel ORA_DISK_1: starting full datafile backupset channel ORA_DISK_1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf channel ORA_DISK_1: starting piece 1 at 20140125 16:29:02 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 16:29:02 channel ORA_DISK_3: starting full datafile backupset channel ORA_DISK_3: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf channel ORA_DISK_3: starting piece 1 at 20140125 16:29:02 channel ORA_DISK_4: starting full datafile backupset channel ORA_DISK_4: specifying datafile(s) in backupset input datafile fno=00004 name=/oradata/orcl/users01.dbf channel ORA_DISK_4: starting piece 1 at 20140125 16:29:02 channel ORA_DISK_5: starting full datafile backupset channel ORA_DISK_5: specifying datafile(s) in backupset input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel ORA_DISK_5: starting piece 1 at 20140125 16:29:02 channel ORA_DISK_6: starting full datafile backupset channel ORA_DISK_6: specifying datafile(s) in backupset input datafile fno=00007 name=/oradata/orcl/system02.dbf channel ORA_DISK_6: starting piece 1 at 20140125 16:29:02 channel ORA_DISK_6: finished piece 1 at 20140125 16:29:09 piece handle=/oradata/orcl/databak/9qouvdue_1_1 tag=TAG20140125T162902 comment=NONE channel ORA_DISK_6: backup set complete, elapsed time: 00:00:07 channel ORA_DISK_5: finished piece 1 at 20140125 16:29:16 piece handle=/oradata/orcl/databak/9pouvdue_1_1 tag=TAG20140125T162902 comment=NONE channel ORA_DISK_5: backup set complete, elapsed time: 00:00:14 channel ORA_DISK_2: finished piece 1 at 20140125 16:29:19 piece handle=/oradata/orcl/databak/9mouvdue_1_1 tag=TAG20140125T162902 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:17 channel ORA_DISK_4: finished piece 1 at 20140125 16:29:22 piece handle=/oradata/orcl/databak/9oouvdue_1_1 tag=TAG20140125T162902 comment=NONE channel ORA_DISK_4: backup set complete, elapsed time: 00:00:20 channel ORA_DISK_3: finished piece 1 at 20140125 16:29:47 piece handle=/oradata/orcl/databak/9nouvdue_1_1 tag=TAG20140125T162902 comment=NONE channel ORA_DISK_3: backup set complete, elapsed time: 00:00:45 channel ORA_DISK_1: finished piece 1 at 20140125 16:29:54 piece handle=/oradata/orcl/databak/9louvdue_1_1 tag=TAG20140125T162902 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:52 Finished backup at 20140125 16:29:54 Starting Control File and SPFILE Autobackup at 20140125 16:29:54 piece handle=/oradata/orcl/databak/c-1347935162-20140125-12 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 16:29:57 因為只有6個檔案，所以，只實際使用了6個通道。備份時間為57秒（16:29:00至16:29:57），和手工指定6通道時的用時完全一樣。 綜上，我們可以看出，這個並行度的引數與手工指定通道的作用是類似的。只不過一個是由RMAN自動分配，一個由人工指定。 FILESPERSET這個引數又是做什麼用的呢？還是來做實驗。 我們把並行度改回2 RMAN> CONFIGURE DEVICE TYPE DISK PARALLELISM 2 BACKUP TYPE TO BACKUPSET; old RMAN configuration parameters: CONFIGURE DEVICE TYPE DISK PARALLELISM 7 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters: CONFIGURE DEVICE TYPE DISK PARALLELISM 2 BACKUP TYPE TO BACKUPSET; new RMAN configuration parameters are successfully stored 根據我們前邊做實驗的經驗，如果這時執行backup database；命令，會自動通過兩個通道來備份。 如果我們執行 backup database filesperset 2; 又會是什麼結果呢？ RMAN> backup database filesperset 2; Starting backup at 20140125 16:58:48 allocated channel: ORA_DISK_1 channel ORA_DISK_1: sid=158 devtype=DISK allocated channel: ORA_DISK_2 channel ORA_DISK_2: sid=147 devtype=DISK channel ORA_DISK_1: starting full datafile backupset channel ORA_DISK_1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel ORA_DISK_1: starting piece 1 at 20140125 16:58:48 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 16:58:48 channel ORA_DISK_2: finished piece 1 at 20140125 16:58:55 piece handle=/oradata/orcl/databak/9vouvfm8_1_1 tag=TAG20140125T165848 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:07 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00004 name=/oradata/orcl/users01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 16:58:55 channel ORA_DISK_1: finished piece 1 at 20140125 16:59:40 piece handle=/oradata/orcl/databak/9uouvfm8_1_1 tag=TAG20140125T165848 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:52 channel ORA_DISK_2: finished piece 1 at 20140125 16:59:40 piece handle=/oradata/orcl/databak/a0ouvfmf_1_1 tag=TAG20140125T165848 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:45 Finished backup at 20140125 16:59:40 Starting Control File and SPFILE Autobackup at 20140125 16:59:40 piece handle=/oradata/orcl/databak/c-1347935162-20140125-14 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 16:59:43 看到了嗎，加了filesperset 2 這個引數後，每次每通道只讀取2個數據檔案了。最終6個數據檔案，生成了3個備份檔案。 換句話說，每個備份集裡，最多隻能包含兩個原始檔。如果我們設為 filesperset 1的話，由於一個備份集中只能有1個原始檔，所以，實驗環境下的這6個數據檔案就要生成6個備份集了。 驗證一下： RMAN> backup database filesperset 1; Starting backup at 20140125 17:01:01 using channel ORA_DISK_1 using channel ORA_DISK_2 channel ORA_DISK_1: starting full datafile backupset channel ORA_DISK_1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf channel ORA_DISK_1: starting piece 1 at 20140125 17:01:01 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 17:01:01 channel ORA_DISK_2: finished piece 1 at 20140125 17:01:08 piece handle=/oradata/orcl/databak/a3ouvfqd_1_1 tag=TAG20140125T170101 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:07 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 17:01:08 channel ORA_DISK_1: finished piece 1 at 20140125 17:01:43 piece handle=/oradata/orcl/databak/a2ouvfqd_1_1 tag=TAG20140125T170101 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:42 channel ORA_DISK_1: starting full datafile backupset channel ORA_DISK_1: specifying datafile(s) in backupset input datafile fno=00004 name=/oradata/orcl/users01.dbf channel ORA_DISK_1: starting piece 1 at 20140125 17:01:43 channel ORA_DISK_2: finished piece 1 at 20140125 17:01:43 piece handle=/oradata/orcl/databak/a4ouvfqk_1_1 tag=TAG20140125T170101 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:35 channel ORA_DISK_2: starting full datafile backupset channel ORA_DISK_2: specifying datafile(s) in backupset input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel ORA_DISK_2: starting piece 1 at 20140125 17:01:43 channel ORA_DISK_1: finished piece 1 at 20140125 17:01:44 piece handle=/oradata/orcl/databak/a5ouvfrn_1_1 tag=TAG20140125T170101 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01 channel ORA_DISK_1: starting full datafile backupset channel ORA_DISK_1: specifying datafile(s) in backupset input datafile fno=00007 name=/oradata/orcl/system02.dbf channel ORA_DISK_1: starting piece 1 at 20140125 17:01:44 channel ORA_DISK_2: finished piece 1 at 20140125 17:01:44 piece handle=/oradata/orcl/databak/a6ouvfrn_1_1 tag=TAG20140125T170101 comment=NONE channel ORA_DISK_2: backup set complete, elapsed time: 00:00:01 channel ORA_DISK_1: finished piece 1 at 20140125 17:01:45 piece handle=/oradata/orcl/databak/a7ouvfro_1_1 tag=TAG20140125T170101 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01 Finished backup at 20140125 17:01:45 Starting Control File and SPFILE Autobackup at 20140125 17:01:46 piece handle=/oradata/orcl/databak/c-1347935162-20140125-15 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 17:01:47 果然。 現在，我們回過頭來，把當需要備份的檔案個數為質數時，如何在多個通道中分配的實驗做了。 為了滿足這個條件，我們在資料庫中再新增一個表空間，並在該表空間中新增一個數據檔案，從而形成7個數據檔案。 SQL> create tablespace demo datafile '/oradata/orcl/demo01.dbf' size 10M; Tablespace created. SQL> create table demo (id int) tablespace demo; Table created. SQL> insert into demo values(1); 1 row created. SQL> commit; Commit complete. SQL> select file_name,file_id,bytes/1024/1024 "size(M)" from dba_data_files; FILE_NAME FILE_ID size(M) ---------------------------------------- ---------- ---------- /oradata/orcl/system01.dbf 1 400 /oradata/orcl/undotbs01.dbf 2 320 /oradata/orcl/sysaux01.dbf 3 190 /oradata/orcl/users01.dbf 4 21.25 /oradata/orcl/hrtbs01.dbf 5 10 /oradata/orcl/demo01.dbf 6 10 /oradata/orcl/system02.dbf 7 10 7 rows selected. 再回到RMAN中，以手工指定4個通道的方式來進行資料庫備份。 MAN> run { allocate channel c1 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c2 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c3 device type disk format '/oradata/orcl/databak1/%U'; allocate channel c4 device type disk format '/oradata/orcl/databak1/%U'; backup database; release channel c1; release channel c2; release channel c3; release channel c4; }2> 3> 4> 5> 6> 7> 8> 9> 10> 11> released channel: ORA_DISK_1 released channel: ORA_DISK_2 allocated channel: c1 channel c1: sid=158 devtype=DISK allocated channel: c2 channel c2: sid=147 devtype=DISK allocated channel: c3 channel c3: sid=138 devtype=DISK allocated channel: c4 channel c4: sid=137 devtype=DISK Starting backup at 20140125 17:41:56 channel c1: starting full datafile backupset channel c1: specifying datafile(s) in backupset input datafile fno=00001 name=/oradata/orcl/system01.dbf channel c1: starting piece 1 at 20140125 17:41:56 channel c2: starting full datafile backupset channel c2: specifying datafile(s) in backupset input datafile fno=00002 name=/oradata/orcl/undotbs01.dbf input datafile fno=00007 name=/oradata/orcl/system02.dbf channel c2: starting piece 1 at 20140125 17:41:56 channel c3: starting full datafile backupset channel c3: specifying datafile(s) in backupset input datafile fno=00003 name=/oradata/orcl/sysaux01.dbf input datafile fno=00006 name=/oradata/orcl/demo01.dbf channel c3: starting piece 1 at 20140125 17:41:56 channel c4: starting full datafile backupset channel c4: specifying datafile(s) in backupset input datafile fno=00004 name=/oradata/orcl/users01.dbf input datafile fno=00005 name=/oradata/orcl/hrtbs01.dbf channel c4: starting piece 1 at 20140125 17:41:56 channel c4: finished piece 1 at 20140125 17:41:57 piece handle=/oradata/orcl/databak1/agouvi74_1_1 tag=TAG20140125T174156 comment=NONE channel c4: backup set complete, elapsed time: 00:00:01 channel c2: finished piece 1 at 20140125 17:42:12 piece handle=/oradata/orcl/databak1/aeouvi74_1_1 tag=TAG20140125T174156 comment=NONE channel c2: backup set complete, elapsed time: 00:00:16 channel c3: finished piece 1 at 20140125 17:42:27 piece handle=/oradata/orcl/databak1/afouvi74_1_1 tag=TAG20140125T174156 comment=NONE channel c3: backup set complete, elapsed time: 00:00:31 channel c1: finished piece 1 at 20140125 17:42:34 piece handle=/oradata/orcl/databak1/adouvi74_1_1 tag=TAG20140125T174156 comment=NONE channel c1: backup set complete, elapsed time: 00:00:38 Finished backup at 20140125 17:42:34 Starting Control File and SPFILE Autobackup at 20140125 17:42:34 piece handle=/oradata/orcl/databak/c-1347935162-20140125-18 comment=NONE Finished Control File and SPFILE Autobackup at 20140125 17:42:37 released channel: c1 released channel: c2 released channel: c3 released channel: c4 實驗證明，當需備份的檔案數不能均分至多個通道時，RMAN會以一種近似平均的方法來處理。那麼為什麼6個檔案4個通道時，RMAN沒有采用1-1-2-2的方式來使用4個通道呢？個人推測是由於當按這種方式分配時，最多的一個通道上還是要有2個檔案，那麼這時，就不如把6個檔案分配在3個通道上（即2-2-2的分配方式）即節省了通道數，又能保證總體的備份時間不會延長。同時，在進行檔案分配時，檔案的大小，也是其進行分配的一個考慮因素，RMAN會在首先保證各通道處理的檔案個數接近的前提下，使每個通道上分配到的總的檔案大小也儘量均衡。