How variable names are handled
Variable names refer to values that are not part of an expression but are accessed while evaluating the expression.
When used to select a resource, the variable name is a persistent attribute. When used to generate an event, the variable name is usually a dynamic attribute, but may be a persistent attribute. When used to select audit records, the variable name is the name of a field within the audit record.
A variable name is restricted to include only 7-bit ASCII characters that are alphanumeric (a-z, A-Z, 0-9) or the underscore character (_). The name must begin with an alphabetic character.
When the expression is used by the RMC subsystem for an event or a rearm
event, the name can have a suffix that is the '@' character followed by 'P',
which refers to RMC's previous observation of the attribute value. Because
RMC observes attribute values periodically and keeps track of the
previously observed value, you can use this syntax to compare the currently
observed value with the previously observed value. For example, the following
event expression would trigger an event if the average number of processes
on the run queue has increased by 50% or more between observations:
(ProcRunQueue - ProcRunQueue@P) >= (ProcRunQueue@P * 0.5)