Writing custom formulas

Explains how to create and modify custom formulas.

You use the following Tivoli Netcool Performance Manager DataMart modules to create or modify formulas:

Formula Selector to select a formula for editing.
Formula Editor to edit and test formulas.
MIB Browser to display a compiled MIB.
MIB Compiler (optional) to add a new MIB.

Before you begin
What is a formula?
A formula (sometimes called a metric) is a script, written in a proprietary language developed by IBM Corporation. A formula is a collection of object identifiers (OIDs,) functions, and standard mathematical operations applied to a subelement to perform a computation. A formula lets you customize the information gathered by Tivoli Netcool Performance Manager DataMart.
Creating formulas
You can create custom formulas to use for discovery and data collection in addition to the formula library included with Tivoli Netcool Performance Manager DataMart.
Standard rules for writing formulas
Describes the standard rules you need to follow when writing formulas.
OIDINST instruction
The OIDINST expression line stores the values of a key for which the expression is true (different from zero.) The instruction is primarily used for Discovery formulas to filter a subset of indexes from a large set, based on properties. If the filter is unsuccessful, the row is skipped. If the filter is successful, the value of the index for the row is assigned to the temporary variable, and processing continues with the next line of the formula.
Types of variables
Returning a result
Only the result of the last line of a formula is returned. This was illustrated in the example formulas. Prior lines made calculations, and manipulated variables, but only the last line returned a result.
Comments in formulas
Syntax for functions
AddForMissing() operator
Using the Formula Selector
You can load an existing formula from the Formula Selector window.
Formula error messages
Understanding the inventory_subelements.txt file
The inventory_subelements.txt file contains the list of rules the Discovery uses. It is located in the conf directory under the PVM directory.

Parent topic: Configuring and Operating DataMart