$db2 backup db nsnpd online to '/backup/nsn'

the backup is started, cd /backup/nsn and ls ,i can find the backup file

$ ls -lt
total 10606476
-rw-r----- 1 db2inst1 db2grp1 2768920576 Feb 19 18:11 NSNPD.0.db2inst1.NODE0000.CATN0000.20080219180901. 001

BUT the backup command failed, return :
SQL2038N A database system error "-2038" occurred during processing.

And Then, i use command ls to check again, found the backup file is missing.

$ db2 list history backup all for nsnpd,show:
Op Obj Timestamp+Sequence Type Dev Earliest Log Current Log Backup ID
-- --- ------------------ ---- --- ------------ ------------ --------------
B D 20080219182323001 N D S0001342.LOG
----------------------------------------------------------------------------
Contains 3 tablespace(s):

00001 SYSCATSPACE
00002 USERSPACE1
00003 NSN_TB
----------------------------------------------------------------------------
Comment: DB2 BACKUP NSNPD ONLINE
Start Time: 20080219182323
End Time: 20080219182717
Status: A
----------------------------------------------------------------------------
EID: 1147 Location: /backup/nsn/dbbak

SQLCA Information

sqlcaid : SQLCA sqlcabc: 136 sqlcode: -2038 sqlerrml: 5

sqlerrmc: -2038
sqlerrp : sqlubBMR
sqlerrd : (1) 0 (2) 0 (3) 0
(4) 0 (5) 0 (6) 0
sqlwarn : (1) (2) (3) (4) (5) (6)
(7) (8) (9) (10) (11)
sqlstate:


Why i can backup this database??