备份错误如下

Starting backup at 26-JUL-08
current log archived
channel t1: starting archive log backupset
channel t1: specifying archive log(s) in backup set
input archive log thread=1 sequence=2129 recid=2119 stamp=661009059
input archive log thread=1 sequence=2130 recid=2120 stamp=661083896
input archive log thread=1 sequence=2131 recid=2121 stamp=661089734
input archive log thread=1 sequence=2132 recid=2122 stamp=661089734
channel t1: starting piece 1 at 26-JUL-08
released channel: t1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of backup command on t1 channel at 07/26/2008

12:03:31
ORA-27192: skgfcls: sbtclose2 returned error - failed to close file
ORA-19511: Error received from media manager layer, error text:
   ANS1312E (RC12)   Server media mount not possible

Recovery Manager complete.

channel t2: starting piece 1 at 27-JUL-08
RMAN-03009: failure of backup command on t1 channel at 07/27/2008

02:07:39
ORA-19502: write error on file "incr_20080727_2815_1", blockno 486913

(blocksize=512)
ORA-27030: skgfwrt: sbtwrite2 returned error
ORA-19511: Error received from media manager layer, error text:
   ANS1312E (RC12)   Server media mount not possible
channel t1 disabled, job failed on it will be run on another channel
RMAN-03009: failure of backup command on t2 channel at 07/27/2008

02:11:27
ORA-19513: failed to identify sequential file
ORA-27206: requested file not found in media management catalog
ORA-19502: write error on file "incr_20080727_2816_1", blockno 49665

(blocksize=512)
ORA-27030: skgfwrt: sbtwrite2 returned error
ORA-19511: Error received from media manager layer, error text:
   ANS1312E (RC12)   Server media mount not possible
channel t2 disabled, job failed on it will be run on another channel
released channel: t1
released channel: t2
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================

RMAN-03009: failure of backup command on t2 channel at 07/27/2008

02:11:27
ORA-19513: failed to identify sequential file
ORA-27206: requested file not found in media management catalog
ORA-19502: write error on file "incr_20080727_2816_1", blockno 49665

(blocksize=512)
ORA-27030: skgfwrt: sbtwrite2 returned error
ORA-19511: Error received from media manager layer, error text:
   ANS1312E (RC12)   Server media mount not possible
RMAN-03009: failure of backup command on t1 channel at 07/27/2008

02:07:39
ORA-19502: write error on file "incr_20080727_2815_1", blockno 486913

(blocksize=512)
ORA-27030: skgfwrt: sbtwrite2 returned error
ORA-19511: Error received from media manager layer, error text:
   ANS1312E (RC12)   Server media mount not possible

Recovery Manager complete.

原因主要有如下:
第一：磁带的空间不够
第二：TSM备份软件出现问题
第三：DRIVER 坏了或者不够用的

这里检查Tivoli Storage Manager(简称TSM)服务器日志后，发现是TSM服务器连接

磁带不正常，重启TSM服务器后，则可以正常备份了。
（具体什么原因导致TSM不能正常工作，可能是因为机房停电后，TSM服务器则不能正常工作）