The job of the word breaker is to take this stream of characters and assemble them into words. This, of course, leads some students to wonder why the index engine would take a Word document which is full of words and make them non-words just to feed them to another process which makes words out of them again. Some students find this scenario pretty funny. The next issue that confuses students is what the actual indexes are and when they are created. When you make modifications to the scope, by adding a new document for example, the words derived from this document are put into a word list.
Word lists reside in memory.
At some point, the word list is written to the disk in what is called the shadow index. A shadow index is called a persistent index because it is written to the disk. The next step is to combine the shadow indexes into the master index. At least once a day, at midnight by default, the master merge occurs automatically and the shadow indexes are merged into the master index. There are some other things that can trigger the master merge, including the administrator forcing the merge to happen.