If 2M+ accounts & implemented Teams or Territory management, any restructuring can result in performance issues. Both sharing components are complex sharing options and result in huge volumes of share records.
Defer Sharing calculations
If you have an object that utilizes sharing and has a large volume of records (such as more than two million accounts), and you must make a bulk change (such as a quarterly realignment requiring a hierarchy change), then there is a feature that Salesforce Support can enable to defer automatic sharing calculations. Natively, every individual change to the role hierarchy, territory hierarchy, groups, sharing rules, user roles, team membership, or ownership of records can initiate automatic sharing calculations. When a bulk change is made, it causes a number of automatic sharing recalculations to begin. By suspending these recalculations temporarily, you are able to make the change and then have sharing calculations happen all at once. This method is typically more efficient and better performing for bulk changes.
Best of single-user owning more than 10,000?
- The user record of the owner should not hold a role in the role hierarchy.
- If the owner's user record must hold a role, put the role at the top of the hierarchy in its own branch of the role hierarchy.
How account Hierarchy impact data access?
Account hierarchy has no impact on data access. it is not a record sharing mechanism.
"A lot of people make a bad assumption when they implement an account hierarchy. They assume the users who can access a parent account can also access the children accounts. The simple fact of only having a parent/child relationship between two records does not drive access. Although the role hierarchy and the territory hierarchy do work in this way, the account hierarchy does not."