A composition unit with name MyApp already exists. Select a different application name.

Problem(Abstract)

A composition unit with name MyApp already exists. Select a different application name.

Cause

This is most frequently observed during the installation or removal of applications, but it may also turn up during other administration tasks such as deleting servers.
The issue maybe caused by WebSphere Application Server APAR PM20642.

In this scenario, if there is an error with the deployment of a module, then this bad deployment is saved, then the WebSphere Application Server configuration will be out of sync.

In WebSphere Process Server, this often happens with a module that has WebSphere Business Integration Adapter Resources that might not be complete or set up properly.
When deploying using WebSphere Integration Developer using "Add Projects", the configuration changes for this bad deployment are automatically saved.

Even after the application is removed, you might not be able to do any further or new application installs or uninstalls (even with a corrected module).

Resolving the problem

The manual workaround is to delete the /blas and /cus directories for the bad application from the configuration.
The resources will be located in the config directory of the profile.:

<profile name>/config/cells/qcell/blas
<profile name>/config/cells/qcell/cus

http://www-01.ibm.com/support/docview.wss?uid=swg21455322
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Thanks and Regards
Bhaskar Ramaraju
http://www.linkedin.com/in/ramarajubhaskar