copyManager Implementation :: in postgreSQL community Driver

Hi All,
there is a copyManager() implementation in community version JDBC driver.
From what I understand from client end, we provide the file as a fileReader
and pass it on to the copyManager() instance.

I see the performance of this copyManager is not comparable to PSQL command
line copy. Hence I wanted to know how differently is copyManager is
implemented?

does copyManager implement the copy command (*in server*) for the whole
file or, it does convert the file data into batches and implement copy
command ?

Regards
Yogi