For BI Presentation Service

In OBIEE - Instanceconfig.xml (Configuration Presentation Services):

<!-- To configure a limited set of locales to be available to users uncomment the <AllowedLocales> tag below
 and choose a subset set of locale tags from the list. Values must be comma separated. -->

<!-- <AllowedLocales>ar-dz,ar-bh,ar-dj,ar-eg,ar-iq,ar-jo,ar-kw,ar-lb,ar-ly,ar-ma,ar-om,ar-qa,ar-sa,ar-so,
ar-sd,ar-sy,ar-tn,ar-ae,ar-ye,cs-cz,da-dk,de-at,de-ch,de-de,de-li,de-lu,el-gr,en-au,en-ca,en-cb,en-gb,en-hk,
en-ie,en-in,en-jm,en-nz,en-ph,en-us,en-za,en-zw,es-ar,es-bo,es-cl,es-co,es-cr,es-do,es-ec,es-es,es-gt,es-hn,
es-mx,es-ni,es-pa,es-pe,es-pr,es-py,es-sv,es-uy,es-ve,fi-fi,fr-be,fr-ca,fr-ch,fr-fr,fr-lu,fr-mc,hr-hr,hu-hu,
id-id,it-ch,it-it,iw-il,ja-jp,ko-kr,ms-my,nl-be,nl-nl,no-no,pl-pl,pt-br,pt-pt,ro-ro,ru-ru,sk-sk,sv-fi,sv-se,
th-th,tr-tr,zh-cn,zh-mo,zh-sg,zh-tw</AllowedLocales> -->

For BI Server

You can find it in the General section of the NQSConfig.INI file.