Problem with restoring the oracle database fialed

Dear All,

I can not use the RMAN script to restore database in Oracle10g.

script 1:
run {
allocate channel t1 type 'SBT_TAPE';
allocate channel t2 type 'SBT_TAPE';
send 'NSR_ENV=(NSR_SERVER=legato, NSR_CLIENT=oracle.dennis.com);
sql 'alter tablespace users offline immediate';
restore tablespace users;
recover tablespace users;
sql 'alter tablespace users online';
release channel t1;
release channel t2;
}

The error message is followoing:
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00558: error encountered while parsing input commands
RMAN-01009: syntax error: found "alter": expecting one of: "parms, ;"
RMAN-01007: at line 7 column 6 file: /oracle_restore.sh

Script 2:
run
{
configure channel device type 'sbt_tape' parms 'ENV=(NSR_SERVER=legato, NSR_CLIENT=oracle.dennis.com)';
restore database until time "to_date('2006-12-01 17:44:55', 'YYYY-MM-DD HH24:MI:SS')";
recover database until time "to_date('2006-12-01 17:44:55', 'YYYY-MM-DD HH24:MI:SS')";
}

The error message is following:
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 12/10/2006 19:02:39
ORA-19554: error allocating device, device type: SBT_TYPE, device name:
ORA-27001: unsupported device type
Additional information: 1

Could you give me any good ideas about the oracle restore?

Thank you very much,
Dennis