FUDforum includes a full text search that allows the user to search the messages posted on the forum by both subject and message body.

When a user posts a message the text of that message is automatically added to the search index, unless you've set your FORUM_SEARCH option to no.

The search index rebuild process will go through every message on the forum and re-index it's data for the search engine. This process, as you can imagine, is VERY CPU intensive and will take a fair amount of time to run. The actual time taken depends on the number of messages you have in your forum.

This process is generally unnecessary, unless you've decided to re-enable the full text search of the forum or have completed an conversion process from a forum other then FUDforum to FUDforum and need to generate a search index of the imported messages.