Clarification sought on deleting connection attributes

Hi,

 From the DBI::DBD docs in "The dbd_db_login6 method" I read:

=====
Here’s how you fetch them; as an example we use hostname attribute,
which can be up to 12 characters long excluding null terminator:

SV** svp;
STRLEN len;
char* hostname;

if ( (svp = DBD_ATTRIB_GET_SVP(attr, "drv_hostname", 12)) && SvTRUE(*svp)) {
    hostname = SvPV(*svp, len);
    DBD__ATTRIB_DELETE(attr, "drv_hostname", 12); /* avoid later STORE */
} else {
     hostname = "localhost";
}
=====

My question concerns the comment saying "avoid later STORE". If I have a 
DBD::ODBC specific attribute which a) may be specified on the connect 
call and b) is copied to any statement handles when they are created and 
c) may also be on a statement handle, should I be calling 
DBD__ATTRIB_DELETE? and what does that "avoid later STORE" really mean?

Martin
-- 
Martin J. Evans
Easysoft Limited
http://www.easysoft.com