Increasing Capacity

Communications Server 2007

Microsoft Office Communications Server 2007 and Microsoft Office Communications Server 2007 R2 will reach end of support on January 9, 2018. To stay supported, you will need to upgrade. For more information, see Resources to help you upgrade your Office 2007 servers and clients.

If you expect your usage needs to grow substantially, you should consider a load-balanced configuration in the beginning. If a load balancer is in place, you can add Communicator Web Access servers to, or remove servers from, an existing deployment without interrupting service. Even users who are participating in IM sessions at the time of the change are unaffected; a load balancer ensures that the same Communicator Web Access server is used for the entire users session.

For details about using a load balancer and connecting servers to it, see Planning for Load Balancing later in this document. For additional information about load balancing, see the Microsoft Office Communications Server 2007 Planning Guide.

This section discusses increasing capacity for current needs and planning for future needs. For information about a study of factors that affect capacity and some adjustments that you can make, see Appendix B: Planning for Capacity Requirements.

Over time, regular monitoring of system usage may reveal that your configuration of Communicator Web Access no longer meets the needs of users during periods of normal usage. The following are some methods for increasing capacity without adding more servers to your deployment:

  • Increasing search thresholds

    Communicator Web Access contains a threshold setting that determines the number of searches that are allowed at one time. This setting is configurable in the global settings for Communicator Web Access. You can use Microsoft Operations Manager 2005 to monitor how often users are reaching this limit. If users continually reach the limit during normal usage, you may want to increase the search limit; however, you need to consider any impact that increasing the limit will have on performance.

  • Optimizing IIS 6.0 scalability

    IIS 6.0, running on the Microsoft Windows Server® 2003 operating system, includes a new architecture and new features to improve scalability on your Communicator Web Access server. For detailed information about optimizing IIS 6.0, see "Improving Scalability by Optimizing IIS 6.0 Queues" at, "Improving Scalability by Optimizing IIS 6.0 Caches" at, and "Additional Resources for IIS 6.0 Scalability" at

  • Adjusting the IIS 6.0 user limit

    By default, IIS 6.0 has a limit of 8,000 connections. This setting is configurable in the following registry key:


    To increase the limit, create a DWORD entry named "MaxConnections" in this location and set an appropriate limit, allowing for a reasonable tolerance for peak periods. For example, if you want to allow 10,000 connections, you would probably set the value at double this number (20,000). For guidance, see the Microsoft Knowledge Base article "Http.sys registry settings for IIS" at

At some point, demand on Communicator Web Access servers may reach the point where increasing search thresholds and optimizing other settings may not prevent degraded performance. If that happens, you will need to consider adding one or more Communicator Web Access servers or upgrading the processing power or memory of existing servers.

  • Adding servers to the Communicator Web Access array

    If your Communicator Web Access servers are configured in a load-balanced array, you can add Communicator Web Access servers to the array as your organization grows without interrupting service. Clients that are participating in IM sessions when the array is changed are unaffected.

  • Adding storage capacity

    Data storage for Communicator Web Access is handled by Office Communications Server 2007. Static data, such as Contact lists and ACLs (access control lists), is stored as persistent data on the Office Communications Server 2007 Back-End Database. If you need to increase data storage capacity, see the Microsoft Office Communications Server 2007 Enterprise Edition Deployment Guide, which is available from the Office Communications Server Technical Library at