Re: Oracle 12.2 logins hang

From: Chris Taylor <>
Date: Tue, 29 May 2018 11:38:07 -0500
Message-ID: <>

Do you have any locked accounts that are being attempted to be logged in to? OR, heavy attempts with invalid passwords?

 There's a known issue where sessions that bang away at locked accounts (or with invalid passwords) cause a basic DoS -like scenario where no users can login.

You may want to turn on login audits to see if you're getting a lot of failed logins for a particular account.

As far as I know this problem still exists in 12c.

High 'library cache lock' Wait Time Due to Invalid Login Attempts (Doc ID 1309738.1)

On Tue, May 29, 2018 at 9:33 AM, Chris Stephens <> wrote:

> Oracle 12.2 on CentOS 7.
> we recently upgraded one of our databases from 12.1 to 12.2 on centos 7.
> we have an application that logs on and logs off for every database
> operation regardless of size. that results in an obscenely high
> connection/disconnection rate which eventually (after several minutes)
> results in all logins to the application account hanging indefinitely on
> "library cache lock". there is no lock holder. the session is attempting
> to update last logon column in sys.user$ (one of the spare columns).
> we are working to address the application issue properly but have
> implemented database resident connection pooling to temporarily alleviate
> the issue. we thought that had the issue licked but it happened again on
> Friday when connection pool was in place. we think there were several
> sessions created outside of the pool by this account earlier in the day or
> the day before but i can't see how that would contribute to the problem.
> we have an SR open with Oracle and have provided systemstate and
> hanganalyze output to them. looking at the hang analyze shows blocked
> sessions waiting on the previously mentioned "library cache lock" but "blocking:
> 0 sessions".
> has anyone seen this before?
> any suggestions on how to work around the issue until we get the
> application code changed to reuse sessions?

Received on Tue May 29 2018 - 18:38:07 CEST

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