Wildcard queries enable you to enter left-truncated, right-truncated and doubly-truncated queries, such as %ing, cos%, or %benz%. With normal indexing, these queries can sometimes expand into large word lists, degrading your query performance.
Wildcard queries have better response time when token prefixes and substrings are recorded in the index.
By default, token prefixes and substrings are not recorded in the Oracle Text index. If your query application makes heavy use of wildcard queries, consider indexing token prefixes and substrings. To do so, use the wordlist preference type. The trade-off is a bigger index for improved wildcard searching.