Processing Occupancy - Avaya Application Solutions Deployment Manual

Processing occupancy

The Busy Hour Call Attempt (BHCA) rate of a system is the total number of calls that are
attempted within that system, during its busy hour. This is distinct from the Busy Hour Call
Completion (BHCC) rate of a system, which counts only those calls that have actually been
completed. The call capacity of a system refers to its BHCC rate.
In Communication Manager products, server occupancy (or processor occupancy, as
applicable) can be broken down into three categories: static occupancy, Call Processing (CP)
occupancy, and system management (SM) occupancy. The static component refers to
keep-alive processes, the CP component refers to processes that are required to set up and
tear down calls (as well as vectoring operations, in the case of call centers), and the SM
component refers to background maintenance operations and system audits. In theory, static
occupancy is a fixed overhead, and CP occupancy is directly proportional to the call rate. SM
occupancy is allocated on an as-needed basis, such as for periodic maintenance functions.
However, if the overall server occupancy exceeds a particular threshold, SM operations are
postponed until a quieter traffic period.
Usually, the relationship between the sum of static and CP occupancy, as a function of BHCC, is
linear, with a positive y-intercept, as illustrated in
Occupancy and BHCC
per call, and the intercept corresponds to the idle (that is, no-load) occupancy. The average
processing cost per call depends on the mix of calls that is being handled by the system, and
how complex each type of call is. For general business calls, nearly all of the CP occupancy is
associated with setting up and tearing down calls. The call processing that is required for
maintaining the call once it has been established is negligible in comparison, regardless of how
long the call lasts. In a call center, the additional cost of processing vectoring steps throughout
the lifetime of a call must also be considered.
Figure 60: Relationship Between Processing Occupancy and BHCC Rate
Idle (No-Load)
Occupancy
Rate. The slope of the line corresponds to the average processing cost
Figure 60: Relationship Between Processing
BHCC Rate
Issue 3.4.1 June 2005
Resource sizing
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