How to Find Blocking Sessions in Enterprise Manager Cloud Control 12c

My friend Franck Pachot noticed that EM12c doesn’t show the blocking sessions across all RAC nodes. Let’s check if we can find them using EM12c. I have connected to first node of our RAC database, created a sample table, inserted a row, committed, and then deleted the row. While the session is open, I opened another terminal, connected to second node and tried to delete the rows in same table so my second session started to wait for the transaction of my first session completed.

blocking sessions menu

I opened the main page of the cluster database, selected “blocking sessions” under the performance menu.


As Franck told, I couldn’t see any blocking sessions although I checked both instances.


I clicked the link for the instance locks, still no lock!


So I clicked “cluster database lock” and voilà! I found my blocking session. It’s for sure that there should be a short cut to reach this page but I couldn’t find it yet. If I found the short cut, I’ll update my blog.

Please share

AWS Big Data Specialist. Oracle Certified Professional (OCP) for EBS R12, Oracle 10g and 11g. Co-author of "Expert Oracle Enterprise Manager 12c" book published by Apress. Awarded as Oracle ACE (in 2011) and Oracle ACE Director (in 2016) for the continuous contributions to the Oracle users community. Founding member, and vice president of Turkish Oracle User Group (TROUG). Presented at various international conferences including Oracle Open World.


  1. Hemant Patel

    Hi Gokhan,

    All I know to get there is from clicking the Performance tab on “Cluster database” then “Database Locks” at bottom of that page. HTH.


    • Gokhan Atil

      Hi Hemant, thanks for feedback. Your method seems shorter and better.

  2. Mr. KemDaiCa

    hello Mr.Gokhan,

    I have an issue related to sending email alert for blocking session in oem 13c. I have create a monitor template and set threshold for blocking session count. I also create a rule set with one rule to track blocking session count metric and action is send email. I apply to on test Oracle Database. After that I saw many blocking session but there are no mail. I can do this with tablespace usage but not for blocking sesion.
    So please guide me how to fix it.

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