A Quick-and-Easy Solution for the Oracle Enterprise Manager (OEM) Unique Domain Identifier Error

While working on adding new targets in Oracle Enterprise Manager utility, I encountered an error:

Target ***_test_domain(weblogic_domain) already exists with Unique Domain Identifier - ***_test_domain.

We get this error because we’re running Oracle Weblogic Cluster on two servers configured with the same Domain (***_test_domain). Here are the following properties used in the configuration:

Product: Oracle Weblogic
Version: 13.5
Forms/Reports Domain: /oracle/domains/***_test_domain
Cluster Servers: test02.***.local and test01.***.local

As a first step towards discovering the configured Weblogic components that exist on these two servers, I verified the test01 server first and used the following path in the OEM:

Setup ==> Add Target ==> Add Targets Manually ==> Add Non-Host Targets Using Guided Process ==> Oracle Fusion Middleware/Weblogic Domain : Oracle Weblogic Domain

These steps lead me to the following page.

Add Oracle Fusion Middleware/Weblogic Domain: Find Targets

I updated the mandatory fields(Administration Server Host, port, Username, Password, Unique Domain Identifier, and Agent) on this page, and the discovery identified the associated targets, which were successfully added without any issues.

However, when I tried a similar activity for the components running on the test02 server, I received the above error. I checked MOS and found the associated note(2301243.1) as follows.

EM 13c: Adding WebLogic Server Target in Enterprise Manager 13c Cloud Control Fails with Error: Target base_domain(weblogic_domain) already exists with Unique Domain Identifier (Doc ID 2301243.1)
SOLUTION
If domain name is different (e.g Financial domain, HR domain - these domains are created by WebLogic Server installations), then Cloud Control allows addition of the new domain target under the the same unique domain identifier. (e.g Farm01_Financial domain, Farm01_HR domain)
Alternatively, as a workaround, use an alias for the conflicting domain name.

The solution of using an alias seems a little misleading; where to use an alias? Or change in a configuration file? It raised quite a few questions. However, I found a simple workaround using a different name for the field “Unique Domain Identifier” on that OEM page, which solved this issue. I used the value of “***_test_domain1” instead of “***_test_domain.” Now all the associated targets are added to the OEM.

To verify the domain added as a target, I used the command line utility in the host servers, confirming the same name exists.

[oracle@test02 bin]$ hostname
test02.***.local
[oracle@test02 bin]$ ./emctl config agent listtargets | grep 'weblogic_domain'
[/***/***_test_domain, weblogic_domain]

[oracle@test01 bin]$ hostname
test01.***.local
[oracle@test01 bin]$ ./emctl config agent listtargets | grep 'weblogic_domain'
[/***/***_test_domain, weblogic_domain]

I hope this quick guide helps you resolve your unique domain modifier error!