Query for importing and exporting data from a database

Hi,

I am using postgres 7.4.2 on Solaris. My unix system does not place a limitation of 2 GB on file size. If I export  a data from my database that causes the file size to be more than 2 GB, then that export fails (and vice versa for importing, i.e. if the file size is more than 3 GB, it can not import). Two questions –

Why does this happen?

Is there any way to avoid this?

Basically, I want to export huge chunk of data to files and then import the same, please help me.

Thanks and regards,

Yateen V. Joshi