To reduce the amount of space used when exporting one can compress the data as creating export file and also import data from a compressed file.

Exporting data directly to a compressed file
#!/bin/ksh

PIPE_FILE=/tmp/exp.pipe
EXP_FILE=exp.dmp.gz

# delete pipe file
rm -f $PIPE_FILE
# create a pipe file
$ mknod $PIPE_FILE p
$ gzip < $PIPE_FILE > $EXP_FILE &
$ exp file=$PIPE_FILE ….

Importing data directly from a compressed file
#!/bin/ksh

rm -f $PIPE_FILE
PIPE_FILE=/tmp/imp.pipe
EXP_FILE=exp.dmp.gz

$ mknod $PIPE_FILE p
$ gunzip < $EXP_FILE > $PIPE_FILE &
$ imp file=$PIPE_FILE ….

If you are using Oracle 10g datapump utility you can’t use the above step as the exdp checks if a file exists before writing and generates an error as the file exists.