PivotTable® Service supports the read-committed and repeatable-read isolation levels (that is, isolated and nonisolated cache modes). By default, the visibility of changes made concurrently by others is read-committed, meaning that only committed updates are visible to a command or query. That is, commits executed by other users are immediately available to PivotTable Service. The repeatable-read isolation level provides a higher degree of isolation. In this mode, the client cache is frozen when a command or query is opened, and remains frozen until the command or query is closed.
You can set the isolation level to isolated using the Default Isolation Mode property.