Bug 33121934 - Library cache lock / load lock / mutex x during connection storm due to update user$

Concurrent logons for user may be affected due to Last Successful Logon Time (LSLT) update:

update user$ set spare6=DECODE(to_char(:2, 'YYYY-MM-DD'), '0000-00-00', to_date(NULL), :2) where user#=:1
(sql_id = 9zg9qd9bm4spu)

REDISCOVERY INFORMATION:
If the concurrent logons for a user may be slow when the system is under
heavy load and/or logon storm happens, all waiting for the Last Successful
Logon Time (LSLT) update to happen, this bug may have been rediscovered.
如果系统处于高负载和/或登录风暴时，用户的并发登录速度可能很慢，所有人都在等待上次成功登录时间 (LSLT) 更新，则此错误可能已被重新发现。

During a connection storm you may see wait events like:
在连接风暴期间，您可能会看到以下等待事件：

• library cache: mutex X
• library cache load lock
• library cache lock
• gc buffer busy acquire

The fix introduces the parameter _disable_last_successful_login_time.
Set it to TRUE to turn off LSLT.
此修复引入了参数 _disable_last_successful_login_time。
将其设置为 TRUE 以关闭 LSLT。

Two hidden system parameters have also been added to optimize LSLT writes in
high load scenarios.
还添加了两个隐藏的系统参数，以优化高负载情况下的 LSLT 写入

 _disable_last_successful_login_time_unlimited_iat - This controls whether
 users associated with a password profile with UNLIMITED Inactive Account
 Time will not have their LSLT updated. 

 _granularity_last_successful_login_time - This controls the granularity
 of LSLT update for _ALL_ users. Say, it is set to 30 seconds and then all
 users logons within that period of 30 seconds will NOT update the LSLT
 for that user.

_disable_last_successful_login_time_unlimited_iat - 这控制与具有无限非活动帐户时间的密码配置文件关联的用户是否不会更新其 LSLT。

_granularity_last_successful_login_time - 控制 ALL 用户的 LSLT 更新的粒度。假设设置为 30 秒，则 30 秒内所有用户登录都不会更新该用户的 LSLT。