N-central Help

Memory service (Local API, SNMP, WMI)

The Memory service monitors the following properties of the physical memory and virtual memory on a device:

  • used memory,
  • free memory,
  • total memory, and
  • memory utilization by the top five processes.

If the Memory service is first being monitored by a probe and then by an agent, the first few scans performed by the probe will measure total memory usage only and not memory utilization by the top five processes. When the agent begins monitoring this service, data will be reported for memory utilization by the top five processes. This may lead to a temporary discrepancy between the results reported by the probe and the agent.

One instance of this service can monitor all of the detected swap files on multiple volumes. The maximum size of a swap file monitored by this service is 16GB.

You can add the Memory service to a monitored device in one of three different types: Local, SNMP, and WMI.

Linux and Mac OS devices frequently trigger a warning or failed state for Physical Memory. This is due to the way the operating system reserves memory and uses buffers. As a result, disable the threshold for Physical Memory on these devices, and configure to alert on Virtual Memory utilization.

Memory service (Local API)

Service Type Local
Instances on a Device 1
Monitored By Windows agent
Scan Interval 60 minutes

Memory service (SNMP)

If a probe discovers a Windows device using SNMP and associates the Memory service to the device, you must manually change the default values assigned for the following:

  • Physical Memory Name - the default assigned value of Physical memory must be changed to Physical Memory as Windows is case-sensitive, and,
  • Virtual Memory Name - the default assigned value of Swap Space must be changed to Virtual Memory.

If you do not make these modifications to the device in SolarWinds N-central, the Memory service will transition to a Failed state.

Service Type SNMP
Instances on a Device 1
Device Class Server - Generic, Workstation - Generic, Other, Switch/Router, Laptop - Windows, Server - Windows, and Workstation - Windows
Monitored By Windows agent, Windows probe
Scan Interval 60 minutes
Physical Memory Index

The SNMP index for the monitored physical memory. You can obtain the index values by performing an SNMP walk on the OID value: .1.3.6.1.2.1.25.2.3.1.3 (hrStorageDescr). You must determine which OID and index value is relevant.

The OID value is contained in the HOST-RESOURCES-MIB definition file.

Physical Memory Name The string corresponding to the row in the hrStorageTable, which describes the type and instance of the table for the Memory (SNMP) service. You can obtain the string by performing an SNMP walk on the OID value: .1.3.6.1.2.1.25.2.3.1.3 (hrStorageDescr).
Virtual Memory Index

The SNMP index for the monitored virtual memory. You can obtain the index values by performing an SNMP walk on the OID value: .1.3.6.1.2.1.25.2.3.1.3 (hrStorageDescr). You must determine which OID and index value is relevant.

The OID value is contained in the HOST-RESOURCES-MIB definition file.

Virtual Memory Name The string corresponding to the row in the hrStorageTable, which describes the type and instance of the table for the Memory (SNMP) service. You can obtain the string by performing an SNMP walk on the OID value: .1.3.6.1.2.1.25.2.3.1.3 (hrStorageDescr).

OID/Calculation

SolarWinds N-central services use Reverse Polish Notation (RPN) for all calculation formulae.

Metric Name OID/Calculation Description
Physical Memory Usage (%) Used Physical Memory/Total Memory * 100 The percentage of physical memory used. This percentage is compared to the thresholds.
Virtual Memory Usage (%) Used Virtual Memory/Total Virtual Memory * 100 The percentage of virtual memory used. This percentage is compared to the thresholds.

Memory Service (WMI)

Service Type WMI
Instances on a Device 1
Device Class Laptop - Windows, Server - Windows, and Workstation - Windows
Monitored By Windows agent, Windows probe
Scan Interval 60 minutes

Properties queried and calculations performed

SolarWinds N-central services use Reverse Polish Notation (RPN) for all calculation formulae.

Namespace root\cimv2
WMI Class Win32_OperatingSystem
WMI Property 0 TotalVirtualMemorySize
WMI Property 1 TotalVisibleMemorySize
WMI Property 2 FreeVirtualMemory
WMI Property 3 FreePhysicalMemory
Scandetail.2.Recipe $VarTotalPhysicalMemSize - $VarFreePhysicalMemSize
Scandetail.3.Recipe [($VarTotalPhysicalMemSize - $VarFreePhysicalMemSize) / $VarTotalPhysicalMemSize] * 100
Scandetail.6.Recipe $VarTotalVirtualMemSize - $VarFreeVirtualMemSize
Scandetail.7.Recipe [($VarTotalVirtualMemSize - $VarFreeVirtualMemSize) / $VarTotalVirtualMemSize] * 100