On 2/4/2015 11:20 AM, ghiureai wrote:
 
Out of memory: Kill process 2090 (ns-slapd) score 954 or sacrifice child

It wasn't clear to me from your post whether you already have a good understanding of the OOM killer behavior in the kernel.
On the chance that you're not yet familiar with its ways, suggest reading, for example this article : http://unix.stackexchange.com/questions/153585/how-oom-killer-decides-which-process-to-kill-first
I mention this because it may not be the DS that is the problem (not saying that it absolutely is not, but it might not be).
The OMM killer picks a process that is using a large amount of memory, and kills it in order to preserve system stability.
This does not necessarily imply that the process it kills is the process that is causing the system to run out of memory.
You said that the DS "crashed", but in fact the kernel killed it -- not quite the same thing!

It is also possible that the system has insufficient memory for the processes it is running, DS cache size and so on.
Certainly it is worthwhile checking that the DS hasn't been inadvertently configured to use more peak memory than the machine has available.

Bottom line : there are a few potential explanations, including but not limited to a memory leak in the DS process.
Some analysis will be needed to identify the cause. As a precaution, if you can -- configure more swap space on the box.
This will allow more runway before the kernel starts looking for processes to kill, and hence more time to figure out what's using memory and why.