Out of memory error during updating huge table

I'm trying to update a table in transaction mode with
300 million records in it, and I'm getting an out of
memory error.

ERROR: out of memory
DETAIL: Failed on request of size 32.

In transaction mode, I first delete all the records in
the table and then try to use COPY to populate it
again with the new data from a file. The out of memory
error happens during the COPY.

Any thoughts? Is there a way to get around this?
Thanks a lot!

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