As a general rule, the directory server performs a case-sensitive search if the attribute on which the search is performed is case sensitive (ces syntax). Similarly, a search is not case sensitive if the attribute on which the search is performed is case insensitive (cis syntax).
However, it is possible to force case-sensitivity over attribute syntax by using the keyword CASE_SENSITIVE=yes in the mapping definition of a table in the nis.mapping file.
For example, the uid attribute has a cis syntax. In this case, for security reasons, it is important to force case sensitivity. Therefore, the passwd.byname definition in the nis.mapping file, includes the CASE_SENSITIVE keyword:
Table: passwd.byname Common: MAP_NAME=passwd.byname # The LDAP attribute used to store the key (uid) is case insensitive! CASE_SENSITIVE=yes