Viewing and adding formulas

You can create formulas and use them in different analyses and in quick analyses.

The Formulas page displays a list of the existing out-of-the-box and custom (user-defined) formulas, and enables you to define new ones. To access the Formulas page, click Administration > DATA WAREHOUSE > Formulas.

Overview of formulas

Formulas enable you to easily aggregate or scale metrics. You can change the scale factor to available metrics or to compute 'derived metrics' by using different options, such as:

A count of events, absolute number
Difference between subsequent samples
Peak counter

The product provides you with some out-of-the-box formulas. With formulas that you define, called custom formulas, you can perform the following calculation and aggregation tasks:

Perform calculations using basic arithmetic operators, using metrics from a single entity
Perform calculations using metrics from a single entity and its parent
Perform aggregation on metrics from children entities
Perform aggregation on subresources (example: BYDISK_**) of a single entity

For example, you can create a formula to calculate the ratio of Powered On VMs over (Total Powered Off) + (Powered Off) VMs for virtual clusters or hosts.

Formulas versus metrics

Formulas are derived from metrics. While they share a lot of similarities, they differ in a few ways. The following table lists the similarities and differences:

¹ Formulas are dynamically computed based on the input metrics, and hence their values are not stored.

² Statistic selection is applicable only when you store data. For formulas, since the data is not stored, and the computation is carried out dynamically when it extracts the input metrics and then does the charting, Statistic selection is not possible for formulas.

Fields and options on the Formulas page

The Administration > DATA WAREHOUSE > Formulas page displays a table with information about each formula. There are two types of formulas listed: Out-of-the-box and User-defined or Custom formulas.

UI element	Description
Formulas table
Formula Name	Internal name of the formula generated by the system using the user-defined name. All custom formula names have a _C suffix.
Formula Label	User-defined name that is used as the label in charts and reports.
Package	Denotes if the formula is in-built or custom.
Actions on formulas
Add formula	Click Add new formula.
Edit formula	Click to edit a formula. You can edit only custom formulas.
Delete formula	Click to delete a formula. You can delete only custom formulas that are not in use. You cannot delete out-of-the-box formulas.

Out-of-the-box formulas

The following table provides details of the out-of-the-box formulas that are available with the product. You cannot modify these formulas.

Name¹	Internal Name	Description	Details	For Target Entity
Cluster queue per processor	F_CLUSTER_QUEUE_PER_PROCESSOR	Calculates the queue length per processor for vSphere cluster	AVG (Host.CPU_READY)	vSphere cluster
Memory Overcommitment	F_MEMORY_OVERCOMMITMENT	Calculates the memory overcommitment in percentage for the vSphere cluster and vSphere host.	SUM (VirtualMachine.TOTAL_REAL_MEM)/<Parent>.TOTAL_REAL_MEM For vSphere cluster parent entity: SUM (VirtualMachine.TOTAL_REAL_MEM)/ Cluster.TOTAL_REAL_MEM For vSphere host parent entity: SUM (VirtualMachine.TOTAL_REAL_MEM)/Host.TOTAL_REAL_MEM	vSphere cluster vSphere host
Spec used	F_SPEC_USED	Calculates the Spec used for the vSphere cluster	SUM (Host.BYBENCHMARK_VALUE[SPECINTRATE2006]) *Cluster.CPU_UTIL	vSphere cluster
Spec configured	F_SPEC_CONFIGURED	Calculates the Spec configured for the vSphere cluster	SUM (Host.BYBENCHMARK_VALUE[SPECINTRATE2006])	vSphere cluster

¹ - This name is displayed as label in charts and reports where the formula is used.

Adding a formula

Navigate to Administration > DATA WAREHOUSE > Formulas.
Click Add new formula.
In the Add a new formula page, specify the following details:
The [confluence_table-plus] macro is a standalone macro and it cannot be used inline. Click on this message for details.
This macro generates standalone content. As a consequence you need to make sure to use a syntax that separates your macro from the content before and after it so that it's on a line by itself. For example in XWiki Syntax 2.0+ this means having 2 newline characters (a.k.a line breaks) separating your macro from the content before and after it.
Click Save. If you receive any validation errors, correct the formula and click Save again.
The formula is saved and is listed in the Formulas page. You can now use it in appropriate analyses, as required.