In Splunk, when a user accesses a dataset in Pivot that lacks persistent acceleration, Splunk automatically creates anad hoc data model acceleration. This temporary acceleration is designed to enhance performance during the user's current session.

According to Splunk Documentation:

"Ad hoc summaries are always created in a dispatch directory at the search head."

"These summaries are temporary and exist only for the duration of the user's Pivot session."

This means that the accelerated data model persists only while the user is actively engaged in the Pivot session. Once the session ends, the ad hoc acceleration is discarded.