Help on copy function

I'm trying to stress PostgreSQL 8beta3 on AIX5.2 with TPCH 1 Go

I have created and configurated a database on 2 tablespaces : first one for
indexes and second one for tables
First script for database creation:

$ more scrCreateDataBase.sh
psql template1<<!
create tablespace dataTbl location '/postgres_data/TpchDataTableSpace';
create tablespace indexTbl location '/postgres_data/TpchIndexTableSpace';
!
createdb tpch
psql tpch<<!
create schema postgres tablespace dataTbl;
!

An example of table script:
$ more cre_tab_part.sql
CREATE TABLE part(
    p_partkey            bigint NOT NULL,
    p_type               varchar(25) ,
    p_size               integer ,
    p_brand              char(10) ,
    p_name               varchar(55) ,
    p_container          char(10) ,
    p_mfgr               char(25) ,
    p_retailprice        decimal ,
    p_comment            varchar(23)
)
;
ALTER TABLE part ADD CONSTRAINT pk_part PRIMARY KEY(p_partkey) USING INDEX
TABLE
SPACE indexTbl;
\q

I populate my database with a shell script which is launching in parallel
each copy statement:
$ more load.sh
for i in `ls *.loader.psql`
do
psql -f $i tpch &
done

An example of copy statement file:
$ more lineitem.loader.psql
\copy lineitem from lineitem.tbl.psql delimiter '|'

And an error occurs :
psql:lineitem.loader.psql:1: ERROR:  could not extend relation
24342131/24342133
/24342324: There is not enough space in the file system.
HINT:  Check free disk space.
CONTEXT:  COPY lineitem, line 1:
"1996-03-13|1|0.04|21168.23|7706|17|N|155190|O|
0.02|1996-02-12|1996-03-22|TRUCK|1|DELIVER IN PERSON|b..."

but my fileSystem has something like 2Go free when copy fails!

Has anybody an explication? Which error I have done?

Thanks

Frédéric GERMANEAU