Whenever I hear "big XML file" I think XML::Twig, as this can efficiently process the XML file record by record without loading the whole thing into memory. The following gives you the desired output. As for your example code, I don't think you can mix XML::XPath with XML::LibXML - I think it'd be best if you use only tried to use the operations provided by XML::XPath.

use warnings;
use strict;
use XML::Twig;
use Data::Dumper;

my $file = 'OpenApi.xml';
my @records;
XML::Twig->new(
    twig_roots => {
        '/nodes/node/children/node/children/node' => sub {
            my ($t, $elt) = @_;
            my $dim = $elt->first_child('dimension');
            push @records, {
                name => $elt->att('name'),
                citype => $elt->att('ciType'),
                status => $dim->att('status'),
                Time => $dim->first_child('body')
                    ->first_child('entry[@key="Last Status Change"]')
                    ->text  };
            $t->purge;
        },
    },
)->parsefile($file);
print Dumper(\@records);
[download]

Update: As for your code, it's just a matter of getting the XPath expression right, this also gives the desired output:

use strict;
use warnings;
use XML::XPath;
use Data::Dumper;

my $bamxml = 'OpenApi.xml';
my $bamxp = XML::XPath->new(filename => $bamxml);
my $bamxpath =  $bamxp->findnodes('//nodes/node/children/node/children
+/node');

my @records;
foreach my $bamnode ($bamxpath->get_nodelist) {
    my $name   = $bamxp->find('./@name',$bamnode)->string_value;
    my $citype = $bamxp->find('./@ciType',$bamnode)->string_value;
    my $status = $bamxp->find('./dimension/@status',$bamnode)->string_
+value;
    my $time = $bamxp->find('./dimension/body/entry[@key="Last Status 
+Change"]',$bamnode)->string_value;
    s/^\s+|\s+$//g for $name,$citype,$status,$time;
    push @records, {
        name => $name,
        citype => $citype,
        status => $status,
        Time => $time
    };
}
print Dumper(\@records);
[download]

Update 2: Oops, missed your requirement "want to read node only where ciType='application'". The same XPath that choroba showed works in my code samples: '/nodes/node/children/node/children/node[@ciType="application"]'

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