run{
allocate channel dup type disk;
sql 'alter system archive log current';
backup format '/u01/app/oracle/duplicate/al_t%t_s%s_p%p' archivelog all;
release channel dup;
}

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of backup command at 02/13/2012 05:04:04
RMAN-06059: expected archived log not found, lost of archived log compromises recoverability
ORA-19625: error identifying file /u01/app/oracle/duplicate/1_33_769179320.dbf
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3

rman> delete archivelog until sequence 38;