Call now: 252-767-6166  
Oracle Training Oracle Support Development Oracle Apps

 E-mail Us
 Oracle Articles
New Oracle Articles

 Oracle Training
 Oracle Tips

 Oracle Forum
 Class Catalog

 Remote DBA
 Oracle Tuning
 Emergency 911
 RAC Support
 Apps Support
 Oracle Support

 SQL Tuning

 Oracle UNIX
 Oracle Linux
 Remote s
 Remote plans
 Application Server

 Oracle Forms
 Oracle Portal
 App Upgrades
 SQL Server
 Oracle Concepts
 Software Support

 Remote S


 Consulting Staff
 Consulting Prices
 Help Wanted!


 Oracle Posters
 Oracle Books

 Oracle Scripts

Don Burleson Blog 







Oracle deadly embrace tips

Oracle Database Tips by Donald BurlesonJanuary 5, 2015

  What is the deadly embrace, or the perpetual embrace?  Does Oracle prevent the deadly embrace, and if so, what errors do I see and how can I prevent them?

Answer:  The deadly embrace often manifests itself as ORA-04020 deadlock detected error.  This is how a deadly embrace happens in Oracle:

1 - Assume that SQL 1 is "holding rows" (via the select for update clause) and is waiting to get more rows that are held by SQL 2.

2 - SQL 2 attempts to update rows that are being held by SQL 1.

3 - Oracle aborts SQL 2 and issues one of these deadlock messages:

Also see these notes on ORA-00054 error, resource busy and NOWAIT specified.

Here are several Oracle deadlock error messages:

ORA-00060: deadlock detected while waiting for resource

Cause: Transactions deadlocked one another while waiting for resources.

Action: Look at the trace file to see the transactions and resources involved. Retry if necessary.

ORA-04020 deadlock detected while trying to lock object

Cause: While trying to lock a library object, a deadlock is detected.  

Action: Retry the operation later.

As we see the perpetual embrace happens when another DML are waiting on resources that are requested by the other, we have the condition knows as the "deadly embrace", and Oracle terminates the DML that causes the embrace.  This perpetual embrace occurs when a session is locking rows using the "for update" clause", which is not a good practice.

Whenever you have competing DML running against the same data, you run the risk of a deadlock. This deadlock condition is an age-old issue known as the "perpetual embrace"!

If your ORA-00060 is caused by competing resources, the perpetual embrace happens when the aborted task (Task B) attempts to lock a row which is being held by another task (Task A), which, in-turn, is waiting for task B to release a lock. To prevent a perpetual wait, Oracle aborts the transaction that caused the deadlock.

The select for update is not a good locking strategy because there are many things that can go wrong.  Instead of select for update, savvy Oracle developers will adopt alternatives mechanisms like a re-read upon update commit where the transaction re-read the rows and ensure that it has not changed since the original read.

If you like Oracle tuning, you may enjoy my bestselling book Oracle Tuning: The Definitive Reference", with over 900 pages of BC's favorite tuning tips & scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



Oracle Training at Sea
oracle dba poster

Follow us on Twitter 
Oracle performance tuning software 
Oracle Linux poster


Burleson is the American Team

Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise. All legitimate Oracle experts publish their Oracle qualifications.

Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  

and include the URL for the page.


Burleson Consulting

The Oracle of Database Support

Oracle Performance Tuning

Remote DBA Services


Copyright © 1996 -  2020

All rights reserved by Burleson

Oracle ® is the registered trademark of Oracle Corporation.