Normally when creating backups you should prefer a RMAN backup. However, this is nog the way to go when you want to transfer a database across an operating system. So say you have an Oracle database on AIX and you want to transfer it to Windows, you should use another method, simply being a dump. I have gathered here the required commands and variables you need just for the dump. If you need a script that creates this, use RMAN backup as an example and work from there.

BACKBACKUPDIR=/var/backup/oracle/schemadump
HOSTNAME=`hostname`
DATESTAMP=$(date +%Y%m%d%H%M)
export ORACLE_HOME=/opt/oracle/product/10.2
DUMP=$BACKBACKUPDIR/$DATESTAMP-${HOSTNAME}-Oracle.dmp
LOG=$BACKBACKUPDIR/$DATESTAMP-${HOSTNAME}-Oracle.log
 
# Connect to the database instance and make the dump as system
${ORACLE_HOME}/bin/exp system/<oraclesyspasswd> FULL=y DIRECT=y FILE=$DUMP LOG=$LOG
/usr/local/bin/tar -cf - $LOG $DUMP | /usr/bin/gzip > $BACKUPFILE
rm $LOG
rm $DUMP

Or without a password in the script:

${ORACLE_HOME}/bin/exp \'/ as sysdba\' FULL=y DIRECT=y FILE=$DUMP LOG=$LOG