Acucobol interface

Hi All,

I'm developing (currently in pre-alfa stage) a Acucobol interface for the
Postgresql.
The Acucobol runtime have a generic FS API interface that handle the work
with the
record oriented files, defining the open, close, read, write and so on low
level function I can
extend the runtime to talk with any file and database.

My current work translate each Acucobol FS command in a relative Postgresql
query and
the returned tuple will be translated in a record oriented view.
After some performance tests I've notice that this path have much overhead
and because
this I was thinking to redesign the interface.

My first think was to bypass the SQL translation and use the Postgresql low
level routines.
I need to see the tables as record oriented archive, so I can scan
sequentially (forward and
backward) each record, lock/unlock it, insert and delete it and start to
read the records with
a match of a specific key.

Does anyone know where can I start to search/read/learn/study some
document/code of the
Postgresql low level routines ?

If need some detail, please ask ;-)!

Thanks in advance.

Roberto Fichera.