class slave wait等待

操作系统：linux RHEL 7.4

数据库：Oracle 12c R2

问题现象：生产中某个核心数据库升级至12cR2后，出现一些“class slave wait”等待事件，且发起用户是sys和customer user，program是后台进程，感觉很奇怪

问题原因：

查询MOS得知

APPLIES TO:
Oracle Database - Enterprise Edition - Version 11.2.0.2 and later
Information in this document applies to any platform.
SYMPTOMS
User Session shows ACTIVE with event "class slave wait". The session type shows BACKGROUND even though its a user session.


SID SERIAL# USERNAME PROGRAM TYPE

PID SPID WAIT_TIME STATE
---------- ---------- ------------------------------ 
------------------------------------------------ ---------- 
------------------------ ---------- -------------------
EVENT
----------------------------------------------------------------
10 1 user1 oracle@psdprod (O000) BACKGROUND
28 6060 0 
WAITING
class slave wait

CAUSE
 

The session logged on with a custom user (lets say user 'user1') while creating the tablespace on ASM disk, does spawns the asm slave processes o000, o001 etc which inherits the user information from parent's state object(which is the user1 session). Since, user1 session will have 'USER1' as the username, the same user information will appear for the slave processes because the slave processes are spawned by the user1 session.

Hence, the slave asm background processes appear with username 'USER1'(logged in user name) in v$session.

SOLUTION
 

No action is needed here. What we are seeing is expected behaviour. Bug 8734260 discussed this issue and this is not a code bug.