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options for Excel Services (discussed in detail in Chapter 7), the actions allowed by the designers and
consumers of the workbooks can be somewhat controlled, which translates into more control over the
anticipated capacity of Excel Services.
Each EWA Web Part creates a session when a workbook is opened and subsequently rendered. As
SharePoint sites, pages, and dashboards are created, the number of EWA Web Parts added to each page should
be monitored closely. The ECS process size can grow and get out of hand very quickly when each
visitor to a site is creating many sessions. By default, the EWA will not explicitly close a session. Instead,
the session life is controlled by the trusted location’s session timeout setting, which could be up to 5
minutes from the last user action if the default settings are still in effect. You can configure each EWA
embedded in SharePoint to reduce the session lifetime, which helps minimize the number of sessions
opened by each user at any point in time. To do this, use the Close Session Before Opening A New One
property exposed through the EWA Modify Shared Web Part feature.
A session is more controllable when you use the Excel Services Web Service. Every API open workbook
call should eventually be followed by a close workbook call. This provides the best session-management
practice because the session will end immediately, thereby releasing ECS resources promptly.
Determining the right amount of EWA functionality for site visitors can go a long way toward getting more
out of the available ECS and WFE resources. You can configure an EWA Web Part to support various levels
of functionality. For example, you can hide the EWA toolbar, which prevents the site visitor from
performing any of the operations that would otherwise be available (such as a calculation or open operation in
Excel). If removing the toolbar completely isn’t appropriate, then leave the toolbar, but remove specific
toolbar menu commands. You can also curtail navigation and interactivity within the grid to suit the needs
of the specific EWA use. You can access these and other features through the EWA Modify Shared Web Part.
Maybe reducing EWA functionality for all visitors to a site is a bit too drastic. Instead, you may want to
use SharePoint permissions to control the functionality allowed by the site users. Using this method, you
can ensure that a certain class of users on the site has less impact on the ECS and WFE because their
permissions restrict the type of operations they can perform when interacting with the EWA.
Another aspect of capacity planning for Excel Services is to determine how many users will be accessing
Excel Services concurrently. The term “concurrently” has a couple of different meanings that should be
The first meaning refers to how many users could be accessing the WFE at the same time, such as
when an e-mail is sent to a large distribution list with a link to a workbook on Excel Services and
many recipients of that e-mail click the link simultaneously (or nearly so). Will the WFE be able to
handle the concurrent client connection load at that point in time? Or do the availability expectations
of the system dictate that it is okay to be unable to service all requests in this type of situation?
The second meaning refers to how many active users could be using the system at the same time. This
scenario targets the day-to-day peak activity of Excel Services. In this context, all users have at least one
session that is active or has not timed out because of inactivity. For this scenario, the concurrent client
connection load on the WFE remains a point of interest. The ECS is of interest as well, because the number of
sessions available to support the peak activity will impact the ECS process size and CPU as it responds to
the various requests.