VPS resourcers warning dcachesize/oomguarpages

I am running 1 vbulletin forum, 1 wordpress, 2 opencart (e-commerce) and 3 simple html sites

And sometimes i get a warning of:

Dec 04, 2014 12:11:29 AM    Resource    Resource dcachesize green alert on environment 113 example.com current value: 22256812 soft limit: 26210000 hard limit: 26210000    Green zone  dcachesize

Dec 04, 2014 12:18:29 AM    Resource    Resource dcachesize yellow alert on environment 113 example.com current value: 22499725 soft limit: 26210000 hard limit: 26210000   Yellow zone dcachesize

Dec 04, 2014 12:11:29 AM    Resource    Resource oomguarpages yellow alert on environment 113 genesiseries.com current value: 168249 soft limit: 191146 hard limit: 191146  Yellow zone oomguarpages

Dec 04, 2014 12:13:30 AM    Resource    Resource oomguarpages green alert on environment 113 genesiseries.com current value: 116764 soft limit: 191146 hard limit: 191146   Green zone  oomguarpages

My CPU usage:

0.7% CPU Load Average: 0.72, 1.06, 0.86

RAM: 524.6 MB 39%

Free: 819.4 MB

Total: 1.3 GB

What can be happening? what is "dcachesize" and "oomguarpages"?