I have not worked over Windows CE before BUT , if it has registry , open it and be sure to have Oracle characterset is set to
This is done at the following key NLS_LANG under Oracle Main Key , adjust it for all required locations by using find and replace function.
Also be sure that the Windows CE itself supports Arabic language at first.
Oracle is a muti platform database , language inside the database has no direct relation with the hosting operating system and this why Oracle database can reside on a Unix server where Arabic Support at the OS level is nearly 0.
IT Manager For Development
Oracle Consultant - OCP