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PRTG Manual: Define Lookups

PRTG uses lookups for some sensors and for other sensors that have custom channels. In general, lookups map status values as returned by a device (usually integers) to more informative expressions in words. Additionally, lookups can define a sensor status based on the status value returned by a device, just like channel limits can define a sensor status. For a printer that returns the status value 1, for example, PRTG can show a sensor in the Warning status with the text message Toner Low instead of only displaying the status value 1.

You can customize lookups by defining your own text messages that a channel shows and by mapping them to a certain sensor status. See section Customizing Lookups.

If a channel uses lookups, you can individually define how to control the status of the sensor, either by using the lookup definition or by using limits for numeric values returned by the device. For more information, see section Channel Settings. It is not possible to use both definitions at the same time.

Lookups do not change data in the PRTG database, they merely change the way a sensor shows a channel. Any change to lookup definition files applies to historic data as well as to live data.

Some exceptions apply to the SNMP Custom String Lookup sensor that basically does an inverse lookup. It does not map an integer to a text message but only looks for matching strings in the lookup definition and shows a status based on this text value.

To upload customized lookups to PRTG Hosted Monitor, see section Manage a PRTG Hosted Monitor Subscription.

In this section:

Requirement: Channel Unit "Custom"

All channels with an enabled Lookup need to use the Channel Unit "Custom". For more information, see section Channel Settings.

There are sensors that provide the Channel Unit "Lookup" in their settings. Do not use the Channel Unit "Custom" for channels of these sensors if you want to use lookups. This results in malfunctioning lookup definitions. For the following sensors, select the Channel Unit "Lookup" in the settings and select the lookup file directly under Channel Lookup during sensor creation:

Visualization of Lookup Channels

PRTG can display channels that use lookups as follows.

Lookup Type	Visualization	Example
SingleInt, Range	Gauge	A Gauge Showing the Status of a Lookup Channel
Boolean	Switch	A Switch Showing the Status of a Boolean Lookup Channel
BitField	Toggles	Toggles Showing the Status of a BitField Lookup Channel

You can view the text messages for the different lookup values by hovering over the respective section.

Gauge Showing the Respective Lookup Message when Hovering over a Color Section

To see which lookup value in which channel shows the Warning or Down status, check the sensor message on a sensor's Overview tab:

Sensor Message on the Overview Tab

We recommend that you stay below 120 lookup values to display visually informative gauges for primary channels. Non-primary channels have an upper limit of around 40 lookup values for gauges.

Gauge Showing 120 Lookup Values

The various sensor states that are displayed in gauges always follow the clockwise order Up < Warning < Down < Unknown. This order stays the same, no matter which numeric value you map to which sensor status in the lookup definition. See the following example:

<?xml version="1.0" encoding="UTF-8"?>
<ValueLookup id="example.lookups" desiredValue="1" undefinedState="olsWarning"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="PaeValueLookup.xsd">
<Lookups>
<SingleInt state="OK" value="1">
Works
</SingleInt>
<SingleInt state="OK" value="2">
Works a bit
</SingleInt>
<SingleInt state="Warning" value="4">
Is slow
</SingleInt>
<SingleInt state="Error" value="8">
Does not work
</SingleInt>
<SingleInt state="OK" value="16">
Works sometimes
</SingleInt>
</Lookups>
</ValueLookup>

Even though the value 8 comes before the value 16, PRTG displays the state OK (shown as the Up status) before the state Error (shown as the Down status).

See Lookups Directory and Format and The XML Schema for more information about the lookup code and format.

Lookups Directory and Format

Lookups are defined in Extensible Markup Language (XML) format in files that end with .ovl. PRTG standard lookup files are located in the \lookups subfolder of the PRTG program directory. PRTG maintains these files. In each of the files, lookups for one or more sensors are defined. Furthermore, the \lookups subfolder contains the \custom subfolder to store your customized lookups.

For a list of all standard lookup files, see section Standard Lookup Files.

The files follow a basic principle. For each numeric value, you can define the following:

A message that the sensor looks up and shows instead of the numeric value.
The status that the sensor shows.

Use the SNMP Custom String Lookup sensor to map a string to a corresponding status. For this purpose, use the lookup type SingleInt.

You cannot access this directory on PRTG Hosted Monitor instances.

The XML Schema

An exemplary schema of the .xml files that contain the lookup definitions can look like this:

<?xml version="1.0" encoding="UTF-8"?>
<ValueLookup id="..." desiredValue="..." undefinedState="..." xmlns="..." xsi="...">
<Lookups>
<SingleInt state="..." value="...">status text</SingleInt>
<SingleInt state="..." value="...">status text</SingleInt>
<SingleInt state="..." value="...">status text</SingleInt>
</Lookups>
</ValueLookup>

Element	Description	Attributes, Value Assignment, and Content
<?xml> content	This is the XML declaration that every .xml file begins with.	version and encoding are 1.0 and UTF-8 respectively content: <ValueLookup>contentValueLookup</ValueLookup>
<ValueLookup> contentValueLookup </ValueLookup>	Defines the ID of the channel, which desiredValue is used, the status for undefined values (undefinedState), and links to the predefined schema definitions in PRTG that allow you to edit lookup files with supported editors.	id: Specifies how the name of the lookup file is shown in the channel settings. PRTG parses the id as a lowercase string. desiredValue: Contains the value that PRTG uses for the calculation of the Coverage. undefinedState: Optionally define a status for values that are not defined in the lookup file. If the target device returns a value that is not included in the lookup definition, the sensor shows this status (OK, Warning, Error, or None) with an according message. Without a definition of undefinedState, the sensor only shows the returned value. xmlns:xsi/xsi: Refers to predefined XML schema definitions in PRTG that allow you to edit lookup files with supported editors. contentValueLookup: Lookup definitions <Lookups>contentLookups</Lookups>
<Lookups> contentLookups </Lookups>	Defines the particular lookups for the sensor data.	contentLookups: One or more lookup entries, see below.
<SingleInt> status text </SingleInt> <Boolean> status text </Boolean> <BitField> status text </BitField> <Range> status text </Range>	Each element defines one lookup entry. There can be one or more lookup entries from the same lookup type. You can use only one kind of lookup type in one lookup file. This means only SingleInt, only Boolean, only BitField, or only Range. Different lookup types in one file are not allowed. The notation for the different lookup types can vary: <SingleInt state="..." value="...">status text</SingleInt> <Boolean state="..." value="...">status text</Boolean> <BitField state="..." value="...">status text</BitField> <Range state="..." from="..." to="...">status text</Range>	state: Defines the status that the sensor shows. Allowed values are OK, Warning, Error, and None. None does not trigger a status change. State values must be capitalized for the sensor to work properly. value: Defines the value that triggers the lookup. Enter an integer. Range always needs both values "from" and "to". status text: Defines a status text that PRTG uses as substitution text and shows instead of the integer, for example, a status message. The SNMP Custom String Lookup sensor maps the status text to one of the specified states. For this sensor, use SingleInt.

Because all .xml files that contain lookup definitions are delivered in a previously specified schema as indicated above, you can customize lookups accordingly.

Example

The following code illustrates the lookup definition for the toner status of the SNMP HP LaserJet Hardware sensor:

<?xml version="1.0" encoding="UTF-8"?>
<ValueLookup id="oid.paessler.hplaserjet.tonerstatus" desiredValue="1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="PaeValueLookup.xsd">
<Lookups>
<SingleInt state="OK" value="0">Toner Okay</SingleInt>
<SingleInt state="Warning" value="1">Toner Low</SingleInt>
<SingleInt state="Error" value="2">No Toner Cartridge Loaded</SingleInt>
</Lookups>
</ValueLookup>

In our example, the lookup file has the following effect:

Value as Reported from HP Printer	Text Shown in PRTG (Channel)
0	Toner Okay	Up
1	Toner Low	Warning
2	No Toner Cartridge Loaded	Down

Customizing Lookups

To upload customized lookups to PRTG Hosted Monitor, see section Manage a PRTG Hosted Monitor Subscription.

If you want to change the status definitions of a channel, follow these steps:

Find out the (file) name of the default lookup file in the settings of the channel that you want to change the status definitions for.

From the \lookups subfolder of the PRTG program directory, copy this file into the \lookups\custom subfolder. Make sure that you do not change the file name.
OR
create a new .ovl file there.
If you use the same ID in the ValueLookup tag, the files in the \lookups\custom subfolder have a higher priority than the original files in the \lookups folder. This way, PRTG prefers your customizations to the original lookup settings. If you want to use custom lookup definitions in addition to the standard lookups, define a new ID in the lookup file that is not used by any other lookup file. PRTG identifies lookup definitions via this ID, it does not use the file name.

Open the file with an XML or text editor and customize the lookups as you like. You can define your own text messages or customize sensor states for specific return values. For example, if you do not want a sensor to show the Down status for the return value 2 but only the Warning status, replace the state Error with Warning.

All possible states are specified in the LookupState.xsd file in the custom directory. Follow the schema of the .xml files that are delivered with PRTG to make sure that you safely edit lookups.

If you import an .oidlib file that contains lookups (you can see this in section Lookup in MIB Importer), you can define your own sensor states for the returned values. If you add an SNMP Library sensor and use this .oidlib file, PRTG creates a lookup definition file that uses the lookupname of the chosen library as id parameter. Override this lookup definition with your own custom lookup as described in this section. This is important because lookups that you add via an .oidlib file do not contain any status definitions and result in the Warning status of the sensor by default because of the entry undefinedState="Warning".

If you use an SNMP Custom String Lookup sensor, you can create a new custom lookup definition in the \lookups\custom subfolder with the expected return values. In this case, use the lookupname of the chosen library as id parameter to override the lookups from the .oidlib file.

When you save an edited lookup, make sure that you save it as an .ovl file. Otherwise, the lookup might accidentally be saved as a .txt file and might not be loaded.

Example for Lookups Customization

For example (for illustration purposes only), imagine you want

the sensor to show the Warning status for all undefined values that the target device might return,

to change the shown status for the return value 2 from the Down to the Warning status, and
to add the state None (shown as the Unknown status) to the example above.

Then take the following steps:

Copy the file oid.paessler.hplaserjet.tonerstatus to the \lookups\custom subfolder of the PRTG program directory.
Open this file with a text editor.
Leave the id value unchanged to prioritize the customized lookup file.
Insert the status definition for undefined values into the ValueLookup element: undefinedState="Warning"
Replace the state Error with Warning for value 2.
Add a SingleInt element with the state None for the (hypothetical) return value 3.
Save the file and reload the custom lookup folder in PRTG.

The customized lookup file looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<ValueLookup id="oid.paessler.hplaserjet.tonerstatus" desiredValue="1" undefinedState="Warning" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="PaeValueLookup.xsd">
<Lookups>
<SingleInt state="OK" value="0">Toner Okay</SingleInt>
<SingleInt state="Warning" value="1">Toner Low</SingleInt>
<SingleInt state="Warning" value="2">No Toner Cartridge Loaded</SingleInt>
<SingleInt state="None" value="3">Unknown Status of Toner</SingleInt>
</Lookups>
</ValueLookup>

See also the SNMP Custom String Lookup sensor for a lookup definition that maps a string value to a sensor status.

desiredValue Attribute

It is necessary to define a desiredValue in the lookup files. The desiredValue corresponds to a status value that triggers a lookup. PRTG calculates the percentage of time this specific status was monitored. PRTG displays the result for all data tables and graphs that show averaged values.

Considering the example above where the desiredValue is 1, PRTG calculates the percentage of time that the toner status showed the Warning status. If, during a time span of five minutes, four of five sensor scans returned Warning, PRTG shows an average of 80% for this time span because 80% of the time, the sensor showed the Warning status.

The desiredValue attribute always has to be an integer. For the lookup type Range, use an integer that you defined for one of your "from" or "to" parameters in the lookup file.

For more information, see the Knowledge Base: Can I graph text values?

Lookup Types: SingleInt, Boolean, BitField, Range

Besides the lookup type SingleInt as seen above, there are three other lookup types: Boolean, BitField, and Range. Using these types, you can define lookup values beyond simple integers.

Lookup Type	Description	Syntax
SingleInt	Use an integer to define a lookup for one status value.	value="int" PRTG supports the full 32-bit integer range.
Boolean	Use 0 or 1 to define a lookup for two different status values.	value="0" value="1"
BitField	Use a bitfield for multiple status values.	Only use this lookup type if you have some basic knowledge of bitmasks. See section More for a general introduction. Every value has to be zero (0) or has to equal a power of two (for example, 1, 2, 4, 8, 16, 32, 64, etc.). The SNMP Custom String Lookup sensor does not support BitFields.
Range	Use an inter range from-to to define a lookup for several status values.	from="int" to="int" Using ranges, the parameters "from" and "to" must always be defined. If you want to query only one single value in a range file, this value must be set as a parameter for "from" and "to" (for example, from="2" to="2"). The SNMP Custom String Lookup sensor does not support ranges. The full 32-bit integer range is supported. For more information, see the Knowledge Base: Custom lookup range.

You can use only one kind of lookup type in one lookup file. This means, only SingleInt, only Boolean, only BitField, or only Range. Different lookup types in one file are not allowed.

Define Lookup Files in Channel Settings

For each sensor with a custom channel, you can define a lookup file to use with the option Lookup in the channel settings. This option is visible for many SNMP sensors, some application sensors, and always for the following sensors:

EXE/Script
EXE/Script Advanced (if you define a Custom unit)
SNMP Custom

For more information, see section Channel Settings.

Loading Lookups

You can (re)load the lookups in the custom folder by going to Setup | System Administration | Administrative Tools in the PRTG web interface and clicking Go! under Load Lookups and File Lists.

A sensor whose lookup file you have modified and reloaded does not re-evaluate this lookup before the next sensor scan. For sensors with long scanning intervals, use the Scan Now option from the context menu to immediately apply the new lookup definition and to avoid an incorrect sensor status.

Debugging

What happens if...

a return value is defined in the lookups that is never returned by a device because the value is not assigned? The value is never triggered, so PRTG ignores this entry.
PRTG receives a return value that is not defined for lookups? No substitution message can be found. PRTG only shows the return value. You can optionally define a status for unknown values with a definition of undefinedState in the ValueLookup element (see section The XML Schema).
different lookup types are in one lookup file? This is not allowed and PRTG discards this lookup definition. If you use miscellaneous lookup types in one file, for example, ranges and SingleInts together, PRTG creates a ticket when loading lookups or restarting the PRTG core server with the following error message: Lookup file "[...]" could not be loaded ("" is not a valid integer).
XML code is incorrect? PRTG creates a new ticket when it loads lookups or restarts the PRTG core server with a corresponding error message and discards this lookup definition.
a lookup file has a file extension other than .ovl? The file is not loaded.
alerting is disabled or based on limits? Error and Warning states that are defined in the lookup do not apply. Make sure that you select the option Enable alerting based on lookups in the channel settings if you want to use lookup definitions to control the sensor status.
you define a scaling factor in channel settings? This does not modify the values that are defined by lookups. Any applied lookup always uses the raw value as retrieved from the target device. If you use a scaling factor for such a channel, you notice the scaling in data graphs but the channel value appears unmodified in data tables.