You can use DSCC to perform this task. For information, see Directory Service Control Center Interface and the DSCC online help.
Remove all indexes that are configured for an attribute.
$ dsconf delete-index -h host -p port suffix-DN attr-name |
For example, the following command deletes all indexes for the preferredLanguage attribute:
$ dsconf delete-index -h host -p port dc=example,dc=com preferredLanguage |
Take great care when deleting default indexes because it can affect Directory Server functioning.