Oracle Database 12.1 introduces a new feature, Concurrent Statistics Gathering.
Concurrent statistics collection is simply the ability to gather statistics on multiple tables, or table partitions, at the same time. When CONCURRENT statistics gathering is enabled, you can execute each statistics gathering job in parallel. This combination is useful when you need to analyze large tables, partitions, or subpartitions. This is accomplished using a combination of the job scheduler, advanced queuing and resource manager. Concurrent statistics collection can reduce the time it takes to gather statistics, provided the system can accommodate the extra workload.
Functionality wise, it is a way to gather stats on multiple tables, table partitions or subpartitions at the same time.
From a user perspective, the concurrent statistics collection functionality is very simple. You set the CONCURRENT global preference to the required value using the DBMS_STATS package. The RDBMS determines if concurrency is appropriate and if so, the level of concurrency to use.
See MOS Note: 2034376.1, How to avoid ORA-06512 and ORA-20000 when Concurrent Statistics Gathering is enabled. New in 12.1 Database, Concurrent Statistics Gathering, Simultaneous for Multiple Tables or Partitions