libpq or ESQL

We are migrating from INFORMIX to POSTGRES;

Currently we use the following code (for both INFORMIX and POSTGRES,) to
connect to the database:

EXEC SQL CONNECT TO :acDatabase AS CONNECTION_MAIN;

If we need to cancel an SQL request in INFORMIX we call;

sqlbreak();

This interrupts the database server and cancels any SQL statement currently
running.

As I understand it POSTGRES uses the libpq functions of:

PQgetCancel, PQfreeCancel and PQcancel.

However if we've used the above 'CONNECT TO' method to connect to the
database we don't have a PGconn connection object which is used by
PQgetCancel.

My question is therefore, should we be using libpq C function PQconnectdb to
connect to the database which will return us the PGconn connection object to
use in PGgetCancel, or is there anotherway to interrupt the database server?

I should note that this is a multi-threaded application running on AIX 6.1.
The WARNING box in the POSTGRESQL guide says that "On Uunix, forking a
process with open libpg connections can lead to unpredictable results..." If
this is the case how should the database server be interrupted?

Thanks to all in advance.

Atif