Configuring Defer Sharing Calculation

Steps:

1. Contact salesforce.com Customer Support to enable Defer Sharing Calculation.
2. Once the feature is enabled, users with “View Setup and Configuration” permission will see the “Defer Sharing Calculations” link in Setup. This link takes you to the Defer Sharing Calculations page shown below.
3. To see the Suspend, Resume, and Recalculate buttons on this page, users must also have the “Manage Sharing Calculation Deferral” permission. Creating a permission set allows you to easily assign this permission to all users who require access to these buttons.

Note: This permission also grants the users who receive it the “Manage Users,” “View Setup and Configuration,” and “Reset User Passwords and Unlock Users” permissions, so it is a powerful permission that should be restricted to a few senior administrators.

Using the Defer Sharing Calculation Feature

The controls on the Defer Sharing Calculations page allow you to:

• View the current state of group membership and sharing calculations
• Suspend group membership calculations, which will also suspend sharing rule calculations, or suspend only sharing rule calculations
• Perform all of your planned changes to roles, groups, queues, and sharing rules quickly while calculations are suspended
• Resume the calculation of group membership or sharing rules

When you resume group membership and sharing calculations after making many changes in an organization with large data volumes, those calculations might take a long time to complete. Changes to group membership are calculated automatically when you resume the calculations, but changes to sharing rules are not. You can use the Recalculate button to ensure that all changes to sharing rules have taken effect. Until you click this button, users might not have the access that you have specified in your sharing rules, and they might continue to have access that you intended to remove.

Note: When you suspend group membership calculations, the system must recalculate all sharing rules, even if you did not add, delete, or modify any sharing rules. This is because the changes that make to groups might affect some or all of the “Owned by members of” or “Share with” groups specified in your sharing rules.

Remember that when group membership or sharing rule calculations are suspended, any administrators performing operations on roles, groups, queues, or sharing rules will discover that their changes have not taken effect. To develop good coordination between administrators—and realistic estimates of the maintenance windows you will need to make large scale changes to your sharing configuration—we recommend thoroughly testing deferred group membership and sharing calculations in a sandbox organization with the data volumes that you anticipate having in production.

When Not to Use Defer Sharing Calculation

Although using Defer Sharing Calculation is a best practice for organizations with large volumes of data, some customers might have so much data that attempting to recalculate all sharing changes at once is not feasible or takes an impractical amount of time. These customers might find that allowing sharing calculations to proceed normally while they configure and load data into their organizations provides the best overall throughput for their organization.

Ref: https://developer.salesforce.com/blogs/engineering/2013/08/extreme-force-com-data-loading-part-6-taking-advantage-of-deferred-sharing-calculation.html