统计信息 STREAMS AQ: WAITING FOR MESSAGES IN THE QUEUE

描述：数据库xtts迁移后，通过该命令EXEC DBMS_STATS.gather_database_stats(degree => 16);收集全库的统计信息，执行上之后就没再看，但是到了第二天
发现数据库的相关收集作业还在执行，比较奇怪。
然后，查询了数据库的相关阻塞和阻塞进程的相关event发现了一个比较奇怪的阻塞。streams aq: waiting for messages in the queue
后续手动测试发现只收集一个表的统计信息也是很慢，然后我杀掉了阻塞的会话，不开并行收集，能很快收集完毕。
怀疑碰到了bug
检查mos上的相关bug和文档发现如下资料：

Bug 33764919 - stats collection stuck on 'streams aq: waiting for messages in the queue' (Doc ID 33764919.8)
Concurrent DBMS_STATS Is Hanged By 'Streams AQ: waiting for messages in the queue' (Doc ID 2727024.1)
Bug 32114729 : CONCURRENT DBMS_STATS IS HANGGED BY 'STREAMS AQ: WAITING FOR MESSAGES IN THE QUEUE'
解决办法：
exec dbms_stats.set_global_prefs('CONCURRENT','FALSE');

#######################################################################################################################
Version 19.3.0.0.0 and later

DBMS_STATS is hanged if current_user is changed before executing DBMS_STATS.

ex)
connect /as sysdba
alter session set current_schema=<USER>;
BEGIN DBMS_STATS.GATHER_TABLE_STATS(
      ownname => '<USER>',
      tabname => '<TABLE>',
      estimate_percent => '10',
      granularity => 'AUTO',
      cascade => TRUE,
      force => TRUE  );
END; 

A preference CONCURRENT is ALL and the concurrent stats is enabled.

SQL> select DBMS_STATS.GET_PREFS('CONCURRENT') from dual;

DBMS_STATS.GET_PREFS('CONCURRENT')
--------------------------------------------------------------------------------
ALL

When the issue is occurring, a session is waiting for 'Streams AQ: waiting for messages in the queue'.

WAIT #140497090265352: nam='Streams AQ: waiting for messages in the queue'

Workaround
Disable concurrent stats gathering.
  
exec dbms_stats.set_global_prefs('CONCURRENT','FALSE')