in amanda.conf
i config like this

tapedev "file:/home/amanda/holding/"

and it should store data in the directory specified above, but when i run    
amdump,i got the following message

DISK planner dev2 /usr/local/samba
START planner date 20030520
INFO planner Adding new disk dev2:/usr/local/samba.
START driver date 20030520
ERROR taper no-tape [not an amanda tape]
FINISH planner date 20030520
STATS driver startup time 0.217
FAIL driver dev2 /usr/local/samba 20030520 0 [can't switch to incremental dump]
FINISH driver date 20030520 time 0.224

how could I solve this problem？