hot backup confusion??

I have 2 AIX boxes. Everything is almost the same on on both boxes.
The only difference is that one contains the production
database and the other contains QA database. The one that
contains the production box has 5 CPU's and the QA Box
has 2 CPU's

I have been using hot backup for the production database for the past 1 year.
Yesterday, I decided to do hot backups in the QA database but I had problems.
The same host copy syntax that I use in production for the hot backup does
not work in QA

BELOW IS WHAT HAPPENED

IN THE PRODUCTION ENVIRONMENT
=============================

#1. SQL> select file_name, tablespace_name from dba_data_files where tablespace_name in ('SYSTEM');

FILE_NAME TABLESPACE_NAME
------------------------------------------------- ----------------
/PRDU1/oraPRD1/PRDDATA/system_PRDDATA01.dbf SYSTEM

#2. SQL> alter tablespace system begin backup;

Tablespace altered.

SQL> host copy /PRDU1/oraPRD1/PRDDATA/system_PRDDATA01.dbf SYSTEM /PRDBACUP

SQL> alter tablespace system end backup;

Tablespace altered.

FROM THE QA ENVIRONMENT
=======================

#1. SQL> select file_name, tablespace_name from dba_data_files where tablespace_name in ('SYSTEM');

FILE_NAME TABLESPACE_NAME
---------------------------------------- ---------------
/QAU1/oraQA1/QADATA/system_QADATA01.dbf SYSTEM

#2. SQL> alter tablespace system begin backup;

Tablespace altered.

SQL> host copy /QAU1/oraQA1/QADATA/system_QADATA01.dbf /QAU1/testing
/usr/bin/ksh: copy: not found.

NOTE: Amazingly in QA when I changed the host copy command to host cp (based on the advice from the board), the hot backup worked

#1. SQL> select file_name, tablespace_name from dba_data_files where tablespace_name in ('SYSTEM');

FILE_NAME TABLESPACE_NAME
------------------------------------------------- ------------------------------
/QAU1/oraQA1/QADATA/system_QADATA01.dbf SYSTEM

#2. SQL> alter tablespace system begin backup;

Tablespace altered.

SQL> host cp /QAU1/oraQA1/QADATA/system_QADATA01.dbf /QAU1/testing

SQL> alter tablespace system end backup;

Tablespace altered.

NOTE:

O/S is IBM AIX
DB is ORACLE 8.1.7.0.0

CAN anyone explain?