In fact starting version 6.0.4, searches containing an underscore should work again.

But you may need to run a reindex first as outlined below.

See section 'Searches that contain an underscore character might not return the correct results' in article 'Workarounds and Limitations: Known issues in DNG 6.0.4':

https://jazz.net/library/article/89437#38

There is a workaround described in this article that resolves the problem:
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Workaround
Starting in version 6.0.4, searches that contain the underscore character should work properly. However, if you upgrade or migrate data from a release earlier than 6.0.4, an administrator must reindex the text indexes. This operation can take a significant amount of time depending on the repository size.

For details about reindexing only the text store indexes, see Repository tools command to regenerate indexes. For a quick summary of reindexing only the text store indexes, see the following examples.

Windows
Open a command prompt and enter the following command:
cd C:\Program Files\IBM\JazzTeamServer\server\
repotools-rm.bat -reindex teamserver.properties=conf\rm\teamserver.properties scope=search

Note: Remember to include scope=search; otherwise, the Jena triplestore will be indexed and the process will take much longer.

UNIX
Open a command prompt and enter the following command:
cd opt/IBM/JazzTeamServer/server/
./repotools-jts.sh -reindex teamserver.properties=conf/jts/teamserver.properties scope=search

Note: Remember to include scope=search; otherwise, the Jena triplestore will be indexed and the process will take much longer.
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