Is there a way to capture the RTC free memory over time ?

 If you have concern on the Java heap size usage, you can think about to enable GC log and use Garbage Collection and Memory Visualizer to analyze the memory usage.

I have a Perl script which I use to periodically gather memory statistics and use the results to post to a web page.  I based it off other Perl scripts that have been shared here. 

Here is a similar framework:  https://jazz.net/library/article/1017

Here is the snipped that gets some of the info:

#!/usr/bin/perl
use XML::XPath;
 use XML::XPath::XMLParser;
use Data::Dumper;
use XML::Simple;
use Carp;
use LWP::UserAgent;
# this is not the complete file, only for demonstration purpose
sub getServiceInfo {

my ($JazzUser,$JazzPass,$JazzURI)=@_;

    my $browser = LWP::UserAgent->new();
    my $ur=$JazzURI;
    $ur =~ s/\/rootservices//;
    $browser->cookie_jar({ file => "$ENV{HOME}/.cookies.txt" });
    push @{ $browser->requests_redirectable }, 'POST';
    $response = $browser->get( $ur . "/secure/service/com.ibm.team.repository.service.internal.webuiInitializer.IWebUIInitializerRestService/initializationData");
    $response = $browser->post( $ur . "/j_security_check", [ j_username =>
$JazzUser, j_password => $JazzPass ], );
    carp "$url error: ", $response->status_line unless $response->is_success;
    if ($response->code != 500) {
    $URI = $ur . "/service/com.ibm.team.repository.service.internal.IServerStatusRestService/ServerInfo" ;

    $response = $browser->get($URI);
    $response->{'_content'};
    }
    else {
    "";
    }
}

# main program
my ($id,$pw,$url);#=@ARGV;
$id="a_jazz_admin_user_id";
$pw="the_password";
%friends=();
%srvrs=();
$collected_secs=time();
$collected_at=scalar localtime($collected_secs);
$| = 1;
print "<h2>Jazz Server Status Collected $collected_at</h2>\n";
#print "<table class='basic-table' cellspacing='1' cellpadding='0' 'border='0'>
#<tr class='blue-med-dark'><th>URI</th><th>Version</th><th>Up Since</th><th>JVM Max</th><th>JVM Used</th><th>JVM Free</th></tr>\n";
$n=0;
while (<>) {
   chomp;
   $url="https://".$_."/rootservices";
   $host_port_contxt=$url;
   #$srvrs{$host_port_contxt}->{'version'}=getVersion($id,$pw,$url);
   #$srvrs{$host_port_contxt}->{'name'}=getName($id,$pw,$url);
   $info=getServiceInfo($id,$pw,$url);
   if ($info ne "" ) {
      $srvrs{$host_port_contxt}->{'metrics'}=$info;
   }
#   print Dumper ($srvrs{$host_port_contxt});
    if (exists($srvrs{$url})) {
    $xp = new XML::XPath($srvrs{$url}->{'metrics'});
    $mm = $xp->find("/soapenv:Envelope/soapenv:Body/response/returnValue/value/maxMemory");
    foreach $x ($mm->get_nodelist) {
        $maxMemory=$xp->getNodeText($x)/1048576;
    }
    $tm = $xp->find("/soapenv:Envelope/soapenv:Body/response/returnValue/value/totalMemory");
    foreach $x ($tm->get_nodelist) {
        $totalMemory=$xp->getNodeText($x)/1048576;
    }
    $fm = $xp->find("/soapenv:Envelope/soapenv:Body/response/returnValue/value/freeMemory");
    foreach $x ($fm->get_nodelist) {
        $freeMemory=$xp->getNodeText($x)/1048576;
    }
    $ut = $xp->find("/soapenv:Envelope/soapenv:Body/response/returnValue/value/uptime");
    foreach $x ($ut->get_nodelist) {
        $upTime=$xp->getNodeText($x);
         $collected_secs=time();
#        $upSince = scalar localtime($collected_secs - $upTime/1000);
        ($sec,$min,$hr,$md,$mn,$yr,$wd,$yd,$dst)=localtime($collected_secs - $upTime/1000);
        $upSince = sprintf "%04.4d/%02.2d/%02.2d %0.2d:%0.2d:%0.2d  ",$yr + 1900 ,$mn+1,$md,$hr,$min,$sec;
    }
    $ut = $xp->find("/soapenv:Envelope/soapenv:Body/response/returnValue/value/publicURI");
    foreach $x ($ut->get_nodelist) {
        $URI=$xp->getNodeText($x);
    }
    $ut = $xp->find("/soapenv:Envelope/soapenv:Body/response/returnValue/value/version");
    foreach $x ($ut->get_nodelist) {
        $version=$xp->getNodeText($x);
    }
   if ($n % 2 == 0) {
        $tr="class=\"even\"";
   }
   else { $tr = "" };
   $n=$n+1;
   printf "%s,%s,%s,%.2f,%.2f,%.2f,%d\n",$URI,$version,$upSince,$maxMemory,$totalMemory,$freeMemory,$upTime/1000;
   #printf "<tr %s><td>%s</td><td>%s</td><td>%s</td><td>%.2f</td><td>%.2f</td><td>%.2f</td><td></tr>\n",$tr,$URI,$version,$upSince,$maxMemory,$totalMemory,$freeMemory;
   }
}

As input I hand a file of the URL that I'd like to collect ( e.g.
https://jts01:9443/jts
https://rtc01:9443/ccm
https://rqm01:9443/qm

and so on

Search this site for "ServerInfo" or IStatusRestService to find other possible examples.