使用crosscheck backupset或crosscheck backup之后，提示所有备份集都为available状态，当他执行delete obsolete时，提示有两个文件需要删除。
实际上，obsolete的backupset的状态也会是AVAILABLE的。
对于OBSOLETE的备份集做删除操作，最好是按照如下步骤：
1.crosscheck backupset;或crosscheck backup;
2.report obsolete;
3.delete obsolete;
RMAN> crosscheck backup; using channel ORA_DISK_1 using channel ORA_DISK_2 using channel ORA_DISK_3 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_118_1_896624153.db RECID=109 STAMP=896624154 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_121_1_896624448.arch RECID=112 STAMP=896624449 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_122_1_896624526.spfile RECID=113 STAMP=896624526 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_123_1_896624527.ctl RECID=114 STAMP=896624530 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_11_24/o1_mf_s_896624531_c580jntq_.bkp RECID=115 STAMP=896624532 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_125_1_896807312.db RECID=116 STAMP=896807313 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_11_26/o1_mf_s_896807507_c5fm6orr_.bkp RECID=117 STAMP=896807509 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_127_1_896807515.arch RECID=118 STAMP=896807515 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_128_1_896807543.spfile RECID=119 STAMP=896807543 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_129_1_896807544.ctl RECID=120 STAMP=896807547 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_11_26/o1_mf_s_896807548_c5fm7yvv_.bkp RECID=121 STAMP=896807550 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_131_1_896807869.db RECID=122 STAMP=896807871 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_11_26/o1_mf_s_896808065_c5fmr484_.bkp RECID=123 STAMP=896808068 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_133_1_896808078.arch RECID=124 STAMP=896808078 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_134_1_896808105.spfile RECID=125 STAMP=896808105 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_135_1_896808107.ctl RECID=126 STAMP=896808110 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_11_26/o1_mf_s_896808111_c5fmsjt5_.bkp RECID=127 STAMP=896808112 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_137_1_897123382.db RECID=128 STAMP=897123383 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_11_30/o1_mf_s_897123538_c5q7tn7w_.bkp RECID=129 STAMP=897123540 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_139_1_897123549.arch RECID=130 STAMP=897123549 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_140_1_897123616.spfile RECID=131 STAMP=897123616 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_141_1_897123617.ctl RECID=132 STAMP=897123620 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_11_30/o1_mf_s_897123622_c5q7x768_.bkp RECID=133 STAMP=897123623 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_143_1_897409343.db RECID=134 STAMP=897409344 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_12_02/o1_mf_s_897409479_c5xbpd56_.bkp RECID=135 STAMP=897409484 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_145_1_897409492.arch RECID=136 STAMP=897409492 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_146_1_897409589.spfile RECID=137 STAMP=897409589 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_147_1_897409591.ctl RECID=138 STAMP=897409594 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_12_02/o1_mf_s_897409595_c5xbswyr_.bkp RECID=139 STAMP=897409596 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_149_1_897409811.db RECID=140 STAMP=897409811 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_12_02/o1_mf_s_897410027_c5xc7g0h_.bkp RECID=141 STAMP=897410029 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_151_1_897410038.arch RECID=142 STAMP=897410038 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_152_1_897410156.spfile RECID=143 STAMP=897410156 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/data2/backup/ORCL_153_1_897410158.ctl RECID=144 STAMP=897410161 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/fast_recovery_area/ORCL/autobackup/2015_12_02/o1_mf_s_897410162_c5xccnjn_.bkp RECID=145 STAMP=897410164 Crosschecked 35 objects