sub _open_db { my $self = shift;
warn "_open_db $self $self->{NAME}\n";
    
    # sorted index
    $DB_BTREE->{'flags'} = 0;
    $DB_BTREE->{'compare'} = sub {
        my ($key1, $key2) = @_;
        $key1 <=> $key2;
    };
    if (tie(my %ip_db, 
            'DB_File', 
            $self->{IP_FILE}, 
            O_RDWR|O_CREAT, 
            0644, 
            $DB_BTREE)) {
        # Enable duplicate keys as well
        $DB_BTREE->{'flags'} = R_DUP;
        if (my $stamp_tie = 
            tie(my %stamp_db, 
                'DB_File', 
                $self->{STAMP_FILE}, 
                O_RDWR|O_CREAT, 
                0644, 
                $DB_BTREE)) {
            $self->{IP_DB} = \%ip_db;
            $self->{STAMP_DB} = \%stamp_db;
            $self->{STAMP_TIE} = $stamp_tie;
warn "_open_db OK IP_DB: $self->{IP_DB}" .
    "  STAMP_DB: $self->{STAMP_DB}  STAMP_TIE: $self->{STAMP_TIE}\n";
            return $self;
        }
        else { 
            $Err_Msg = "Can't open stamp db $self->{STAMP_FILE}: $!"; 
        }
warn "_open_db failed $Err_Msg\n";
        untie %ip_db;
warn "_open_db untie complete\n";
    }
    else { $Err_Msg = "Can't open IP db $self->{IP_FILE}: $!" }
warn "_open_db failed $Err_Msg\n";
    return 0;
}

sub close_db { my $self = shift;
warn "close_db $self\n";
    
    delete $self->{STAMP_TIE};
warn "delete STAMP_TIE complete\n";
    untie %{$self->{STAMP_DB}};
warn "untie STAMP_DB complete\n";
    delete $self->{STAMP_DB};
warn "delete STAMP_DB complete\n";
    untie %{$self->{IP_DB}};
warn "untie IP_DB complete\n";
    delete $self->{IP_DB};
warn "delete IP_DB complete\n";
    return 1;
}