Re: Wait Event - enq: IV - contention

From: Jonathan Lewis <>
Date: Tue, 27 Mar 2018 19:11:02 +0000
Message-ID: <LO1P123MB0977DBC66C2ED1483799BD09A5AC0_at_LO1P123MB0977.GBRP123.PROD.OUTLOOK.COM>


You say "databsae reboot".
Is this restarting all 4 instances in turn, or stopping all 4 then restarting them, or just restarting the stuck instance ?

IV is supposed to be "synchronising library cache invalidation" - so the randomness may be due to the luck of which instance a process starts to run on; and if you don't stop all the instances before restarting that might explain why the problem can persist across restarts. This is all conjecture of course, trying to prompt some ideas that I would then check if I had my hands on the system.

Jonathan Lewis

From: <> on behalf of Biju Thomas <> Sent: 27 March 2018 19:56
Subject: Re: Wait Event - enq: IV - contention

Thank you, Jonathan. The user canceled and resubmitted the program and it completed. I checked SGA resize ops, and do not see many resize operations, and there was none during when the program was stuck last time. The odd part is that the problem persists even after a database reboot. Not consistent, on an average 1, out of 8 tries get stuck.

This is an EBS concurrent program. The program has more frequency of getting stuck if the user submits it as part of a "request set". User says it gets stuck almost all the time. If submitted as a single request, it completes most of the time. Still investigating other behaviors.

  • Biju

On Tue, Mar 27, 2018 at 12:52 PM Jonathan Lewis <<>> wrote:

If you convert decimal to Hexadecimal to ASCII:

P1 is just a repeat of the lock information, reading IV, mode 5 P2 is supposed to be an object_id for the IV lock, but yours actually reads "SYNC" P3 = 3

Which node is the process running on ? The IV is supposed to synchronising library cache invalidation across instances. Perhaps P3 = 3 is a large-scale function, perhaps it's saying that this instance is waiting for instance 3 (which might be 4 depending on whether Oracle is counting from 0 or 1 in this case).

One guess: do you see SGA resizes at the time this is happening - perhaps one instance starts resizing and locks up the other instances as it does so.

Jonathan Lewis

From:<> <<>> on behalf of Biju Thomas <<>> Sent: 27 March 2018 18:40
To:<> Subject: Wait Event - enq: IV - contention

Trying to troubleshoot a stuck program. The program gets stuck at a particular wait event 1 out of every 8 runs on an average. When the program completes, it finishes in few minutes. When it is stuck, the P1, P2 values are always the same. Can you please tell what the P1, P2, P3 values represent.

Current Wait Event              enq: IV - contention
Current Wait Class               Other
P1                         type|mode 1230372869
P2                         id1 1398361667
P3                         id2 3
Object                   None

They are not OBJECT_IDs.

Version: Oracle database
RAC Database, 4 nodes.

Thanks for your help.
Biju Thomas



Biju Thomas<>
-- Received on Tue Mar 27 2018 - 21:11:02 CEST

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