How to improve the performance of queries against UNIFIED_AUDIT_TRAIL
Due to the nature of the internal structures used to store the unified audit data, the queries on the UNIFIED_AUDIT_TRAIL view are slow when there are many audit records ( ~1M ).
Development added new functionality to the DBMS_AUDIT_MGMT package to allow the movement of the data from the CLI% structures into a proper table ( having the same columns as the CLI% structures ).
You can read more about this functionality is MOS Note : How To Transfer Unified Audit Records To An Internal Relational Table (Doc ID 2212196.1)