MWI Failure and High CPU Usage on Cisco Unity

Introduction

This document describes one reason why CPU usage for Cisco Unity goes up to more than 90% when Cisco Unity performs Message Waiting Indicator (MWI) dial-out to the Cisco CallManager Express. This document also provides a solution in a Cisco CallManager Express and Cisco Unity environment.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

• Cisco CallManager Express

• Cisco Unity

• Cisco IOS®

Components Used

The information in this document is based on these software and hardware versions:

• Cisco CallManager Express version 3.3

• Cisco Unity version 4.0(5)

• Cisco IOS Software Release 12.3(14)T5 SPSERVICES

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Background

The MinimumMWIRequestInterval parameter is the minimum time between MWIs. It controls the rate at which outgoing serial packets are sent to the phone system. An MWI request frequency under heavy load can cause MWI failure. The MinimumMWIRequestInterval setting works as a switch file parameter to control the rate at which MWIs are sent to the phone system. The setting can prevent MWI failures. By default, this setting is disabled.

Problem

After an upgrade to Cisco Unity 4.0(5), two problems start on Cisco Unity:

• MWI does not function for some users.

• CPU usage for Cisco Unity reaches more than 90%. In order to reduce CPU usage, the only method is to kill the AvNotifierMgr service (see arrow A in Figure 1).

However, Cisco Unity users can still perform these tasks:

• Leave voicemail messages

• Listen to voicemail messages

• Receive email notification

Solution

The solution is to add this text to the Cisco0002.ini file which is located in the \CommServer\InitLib\ folder (see arrow A in Figure 2):

[Configuration]

MinimumMWIRequestInterval=1500

This forces Cisco Unity to wait to dial out the MWI and prevents the MWI from causing looping and collisions.

Related Information

• Voice Technology Support
• Voice and Unified Communications Product Support
• Troubleshooting Cisco IP Telephony
• Technical Support & Documentation - Cisco Systems