</TT
>
       argument is used to refer to the event procedure in error messages.
       This value cannot be <TT
CLASS="SYMBOL"
>NULL</TT
> or a zero-length string.  The name string is
       copied into the <TT
CLASS="STRUCTNAME"
>PGconn</TT
>, so what is passed need not be
       long-lived.  The <TT
CLASS="PARAMETER"
>passThrough</TT
> pointer is passed
       to the <TT
CLASS="PARAMETER"
>proc</TT
> whenever an event occurs. This
       argument can be <TT
CLASS="SYMBOL"
>NULL</TT
>.
      </P
></DD
><