大家好！我遇到一个难题，之前备份好好的在9点左右结束，但是现在变成12点结束，时间多了3个小时左右。
备份代码是：
allocate channel c1 type disk;
allocate channel c2 type disk;
allocate channel c3 type disk;
backup as compressed backupset database plus archivelog delete input;
release channel c1; release channel c2;release channel c3;我查看了rman的备份日志，现象是这样的：3个channel同时备份了archivelog文件用了15分钟左右，生成了3个文件。
备份datafile的时候都是分配好的3个通道都用上，但是首先完成的是channel 3，生成一个文件，用了3个小时。
channel 3再继续压缩备份数据，过了3个小时，channel 1,channel 2,channel 3产生3个文件，都写着花了3小时，这样变成多了3小时。
（datafiel的备份文件之前是3个就好了，但是现在是生成4个文件）。
之前备份datafile最多用5小时接结束的备份，现在变成了3.5+3.5，备份datafile变成了6，7个小时了。不知道为什么非要3个channel最后一起完成，生成最后的3个文件，怎么看我都不了解channel真正的含义。
是不是我的channel不够，需要开4个？假如能在channel 3生成文件后，channel1，2都生成文件就好了，释放掉channel这样应该可以释放资源，channel 3也可以快一点结束备份。
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET;这是rman配置， PARALLELISM是1，我们用的是hdisk30的磁盘（矩阵上几个硬盘映射过来的），这个参数修改成3，和allocate 3 channel有什么特定的关系，可以释放掉其他channel的资源吗？看到现象，找文档还是没能有办法，真的是很难过的一件事情，请大家帮慢解决一下，提提建议。
备份代码是：
allocate channel c1 type disk;
allocate channel c2 type disk;
allocate channel c3 type disk;
backup as compressed backupset database plus archivelog delete input;
release channel c1; release channel c2;release channel c3;我查看了rman的备份日志，现象是这样的：3个channel同时备份了archivelog文件用了15分钟左右，生成了3个文件。
备份datafile的时候都是分配好的3个通道都用上，但是首先完成的是channel 3，生成一个文件，用了3个小时。
channel 3再继续压缩备份数据，过了3个小时，channel 1,channel 2,channel 3产生3个文件，都写着花了3小时，这样变成多了3小时。
（datafiel的备份文件之前是3个就好了，但是现在是生成4个文件）。
之前备份datafile最多用5小时接结束的备份，现在变成了3.5+3.5，备份datafile变成了6，7个小时了。不知道为什么非要3个channel最后一起完成，生成最后的3个文件，怎么看我都不了解channel真正的含义。
是不是我的channel不够，需要开4个？假如能在channel 3生成文件后，channel1，2都生成文件就好了，释放掉channel这样应该可以释放资源，channel 3也可以快一点结束备份。
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET;这是rman配置， PARALLELISM是1，我们用的是hdisk30的磁盘（矩阵上几个硬盘映射过来的），这个参数修改成3，和allocate 3 channel有什么特定的关系，可以释放掉其他channel的资源吗？看到现象，找文档还是没能有办法，真的是很难过的一件事情，请大家帮慢解决一下，提提建议。
Starting backup at 16-FEB-11
current log archived
channel c1: starting compressed archive log backupset
channel c1: specifying archive log(s) in backup set
input archive log thread=1 sequence=19719 recid=35433 stamp=743219209channel c1: starting piece 1 at 16-FEB-11
channel c2: starting compressed archive log backupset
channel c2: specifying archive log(s) in backup set
input archive log thread=1 sequence=19704 recid=35400 stamp=743161873channel c2: starting piece 1 at 16-FEB-11
channel c3: starting compressed archive log backupset
channel c3: specifying archive log(s) in backup set
input archive log thread=2 sequence=15707 recid=35421 stamp=743198799channel c3: starting piece 1 at 16-FEB-11
channel c2: finished piece 1 at 16-FEB-11
piece handle=/oraBackup/AEONCN/backupset/2011_02_16/o1_mf_annnn_TAG20110216T040147_6oopxdt6_.bkp comment=NONE
channel c2: backup set complete, elapsed time: 00:11:07
channel c2: deleting archive log(s)channel c3: finished piece 1 at 16-FEB-11
piece handle=/oraBackup/AEONCN/backupset/2011_02_16/o1_mf_annnn_TAG20110216T040147_6oopxdw6_.bkp comment=NONE
channel c3: backup set complete, elapsed time: 00:11:09
channel c3: deleting archive log(s)channel c1: finished piece 1 at 16-FEB-11
piece handle=/oraBackup/AEONCN/backupset/2011_02_16/o1_mf_annnn_TAG20110216T040147_6oopxdrr_.bkp comment=NONE
channel c1: backup set complete, elapsed time: 00:11:26
channel c1: deleting archive log(s)Starting backup at 16-FEB-11
channel c1: starting compressed full datafile backupset
channel c1: specifying datafile(s) in backupset
input datafile fno=00093 name=+DG1/aeoncn/datafile/undotbs.411.7channel c1: starting piece 1 at 16-FEB-11
channel c2: starting compressed full datafile backupset
channel c2: specifying datafile(s) in backupset
input datafile fno=00143 name=+DG1/aeoncn/undotbs2_02channel c2: starting piece 1 at 16-FEB-11
channel c3: starting compressed full datafile backupset
channel c3: specifying datafile(s) in backupset
input datafile fno=00142 name=+DG1/aeoncn/undotbs2.dbfchannel c3: starting piece 1 at 16-FEB-11
channel c3: finished piece 1 at 16-FEB-11
piece handle=/oraBackup/AEONCN/backupset/2011_02_16/o1_mf_nnndf_TAG20110216T041318_6ooqm14t_.bkp comment=NONE
channel c3: backup set complete, elapsed time: 03:39:58
channel c3: starting compressed full datafile backupset
channel c3: specifying datafile(s) in backupset
input datafile fno=00089 name=+DG1/aeoncn/datafile/undotbs.398.11channel c3: starting piece 1 at 16-FEB-11
channel c2: finished piece 1 at 16-FEB-11
piece handle=/oraBackup/AEONCN/backupset/2011_02_16/o1_mf_nnndf_TAG20110216T041318_6ooqm168_.bkp comment=NONE
channel c2: backup set complete, elapsed time: 03:41:35
channel c1: finished piece 1 at 16-FEB-11
piece handle=/oraBackup/AEONCN/backupset/2011_02_16/o1_mf_nnndf_TAG20110216T041318_6ooqm0bj_.bkp comment=NONE
channel c1: backup set complete, elapsed time: 03:42:11
channel c3: finished piece 1 at 16-FEB-11
piece handle=/oraBackup/AEONCN/backupset/2011_02_16/o1_mf_nnndf_TAG20110216T041318_6op4hjr1_.bkp comment=NONE
channel c3: backup set complete, elapsed time: 03:39:37
Finished backup at 16-FEB-11