when I want Backup OpenERP DB, I see this error:

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Server Traceback (most recent call last): File "/opt/openerp/server/openerp/addons/web/common/http.py", line 592, in send result = openerp.netsvc.dispatch_rpc(service_name, method, args) File "/opt/openerp/server/openerp/netsvc.py", line 360, in dispatch_rpc result = ExportService.getService(service_name).dispatch(method, params) File "/opt/openerp/server/openerp/service/web_services.py", line 117, in dispatch return fn(*params) File "/opt/openerp/server/openerp/service/web_services.py", line 222, in exp_dump data = stdout.read() MemoryError Client Traceback (most recent call last): File "/opt/openerp/server/openerp/addons/web/common/http.py", line 260, in dispatch r = method(controller, self, **self.params) File "/opt/openerp/server/openerp/addons/web/controllers/main.py", line 404, in backup req.session.proxy("db").dump(backup_pwd, backup_db)) File "/opt/openerp/server/openerp/addons/web/common/openerplib/main.py", line 117, in proxy result = self.connector.send(self.service_name, method, *args) File "/opt/openerp/server/openerp/addons/web/common/http.py", line 611, in send raise fault Fault: <Fault : 'Traceback (most recent call last):\n File "/opt/openerp/server/openerp/addons/web/common/http.py", line 592, in send\n result = openerp.netsvc.dispatch_rpc(service_name, method, args)\n File "/opt/openerp/server/openerp/netsvc.py", line 360, in dispatch_rpc\n result = ExportService.getService(service_name).dispatch(method, params)\n File "/opt/openerp/server/openerp/service/web_services.py", line 117, in dispatch\n return fn(*params)\n File "/opt/openerp/server/openerp/service/web_services.py", line 222, in exp_dump\n data = stdout.read()\nMemoryError\n

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I can not understand what's the problem??

Thanks .