Oracle wait events I learnt today

Some New wait events that I learnt today,

acknowledge over PGA limit (12.1)

The "Acknowledge Over PGA limit" is a new wait event that was introduced with PGA_AGGREGATE_LIMIT in 12.1, and it will force a process that wants more PGA to wait a bit if the instance is getting close to hitting the limit. Set or increase PGA_AGGREGATE_TARGET to non zero value and also try to increase "_pga_limit_target_perc" or set PGA_AGGREGATE_LIMIT to zero to disable automatic pga memory management.

enq: IV - contention (No idea)

2028503.1 12c RAC DDL Performance Issue: High “enq: IV – contention” etc if CPU Count is Different “

Not more info found but apparently when impdp run's there's too much of DDL happening and we saw this issue.

Failed Logon Delay (11g)

In Oracle Database 11G there is a new 'feature' related to hacking prevention:

Logon Delays:

A hacker may attempt a brute force hack to break into your Oracle Database. In this case they try constant logons to the database using some form of a word list. Oracle 11g includes a logon delay that takes effect after the third failed password entry attempt. This makes the brute force hacking more difficult. After the third failed logon attempt, Oracle will incrementally delay subsequent logon or password prompts up to a maximum of 10 seconds. No delay will occur if the logon is successful. This is in conjunction with parameters sec_protocol_error_further_action  and sec_protocol_error_trace_action

BUT there is a problem/bug , until OracleDatabase version 11.2.0.2  , You can encounter this bug and experience high library cache contention , when you have both users connecting with good passwords and users connecting with bad passwords

Thanks

Suresh