Explanation: Predefined Database Service Names for Autonomous Transaction Processing
The tnsnames.ora file provided with the credentials zip file contains five database service names identifiable as tpurgent, tp, high, medium, and low. The predefined service names provide different levels of performance and concurrency for Autonomous Transaction Processing.
• tpurgent: The highest priority application connection service for time critical transaction processing operations. This connection service supports manual parallelism.
• tp: A typical application connection service for transaction processing operations. This connection service does not run with parallelism.
• high: A high priority application connection service for reporting and batch operations. All operations run in parallel and are subject to queuing.
• medium: A typical application connection service for reporting and batch operations. All operations run in parallel and are subject to queuing. Using this service the degree of parallelism is limited to four (4).
• low: A lowest priority application connection service for reporting or batch processing operations. This connection service does not run with parallelism.
https://docs.oracle.com/en/cloud/paas/atp-cloud/atpug/manage-priorities.html#GUID-80E464A7-8ED4-45BB-A7D6-E201DD4107B7