In Oracle ADF when we use sortable="true" on af:column By default sorting will be done case-sensitively ,which means that upper case data will be shown first and then lower case data will shown .As shown in below screenshot
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To make this work case insensitively , we can use sortStrength="Primary" attribute on af:column as below
Now my work works case insenstive as below.
Please note this works only with 11.1.1.7 and above version