If you look in the configuration guide you will find that the CASE_SENSITIVE_CHARACTER_COMPARISON parameter in the NQConfig file controls the case sensitive search within OBIEE. Be aware that you might be fooled by your database settings. If you are on an Oracle database 10G+ you can use a connection script in the repository to allow case insensitive searches. Go to the connection pool, click on the connection script tab.
alter session set NLS_SORT=BINARY_CI
alter session set NLS_COMP=LINGUISTIC
Save the repository, reboot the BI-Server
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