如何解决数据长期保留与带库槽位不足之间的冲突？

数据无限期保留时间久了磁带数量越来越多而带库槽位有限。只能去除部分full状态的磁带。
但同步存储池到副本存储池 经常会因为磁带不在带库失败。
ANR1229W Volume 005459L5 cannot be backed up to a copy

     storage pool or copied to an active-data storage pool.-  
     the volume is offline, in use by another process, not    
     currently mountable, or access mode is "unavailable" or  
     "destroyed". (SESSION: 37529)        

求解决方法？？？