Which procedure gathers statistics that are always used in the generation of any execution plan?

The DBMS_STATS.GATHER_DATABASE_STATS procedure is used to gather statistics for all schema objects in the database that do not have up-to-date statistics. These statistics are essential for the optimizer to make informed decisions about the most efficient way to execute a query. The procedure collects statistics such as table and column statistics, index statistics, and system statistics, which are all used in the execution plan generation.

References:

Oracle Database PL/SQL Packages and Types Reference, 19c

Oracle Database Performance Tuning Guide, 19c