密码延迟验证官方文档说明：

Oracle® Database Security Guide 11g Release 1 (11.1)

Preventing passwords from being broken. If a user tries to log in to Oracle Database multiple times using an incorrect password, Oracle Database delays each login. This protection applies for attempts made from different IP addresses or multiple client connections. Afterwards, it gradually increases the time before the user can try another password, up to a maximum of about 10 seconds. If the user enters the correct password, he or she is able to log in successfully without any delay.

This feature significantly decreases the number of passwords that an intruder would be able to try within a fixed time period when attempting to log in. The failed logon delay slows down each failed logon attempt, increasing the overall time that is required to perform a password-guessing attack, because such attacks usually require a very large number of failed logon attempts.

密码延迟验证初衷是为了防止密码在短时间内被暴力破解，随着密码输入错误次数，延迟验证时间会逐步增加一直到最大10s。

如果由于密码延迟验证导致了大量的无event的会话，或library cache lock，可以保证安全前提下，关闭密码延迟验证。

在不同版本可以通过如下设置关闭密码延迟验证：

11g：

# 在spfile中设置event：event = "28401 trace name context forever,level 1"
SQL> alter system set event="28401 trace name context forever,level 1" scope=spfile;
# 针对SYS用户，可以看到在11g中该参数是针对sys用户：
_sys_logon_delay      1     TRUE   failed logon delay for sys     
SQL> alter system set "_sys_logon_delay"=0 scope=spfile;

12c

# 可以看到12c中，该参数已经变更为控制数据库实例，所以可以通过修改该参数关闭密码延迟验证
_sys_logon_delay    1   TRUE   The failed logon delay for the database instance