If you don't specifically need to rely on only
h_vmem then it's possible to use complexes of type
FORCED. You can create a new complex in
qconf -mc called something like
bigmem and make it of type
FORCED. Then you just edit your exec host with
qconf -me and add
bigmem=1 to its complexes section. Now only jobs that are submitted with
-l bigmem will be queued on to that host.
I don't think it's possible to use just
h_vmem because the of the way the relop is defined any host with sufficient memory to satisfy a job's request is eligible, so low memory jobs would still be queued on high memory hosts.