Part of the indexing process in Microsoft Indexing Service. Merges combine word lists into persistent indexes and ultimately into a master index. A merge can be one of several types:
Shadow merge:
Combines word lists into persistent indexes called shadow indexes in order to free server resources and increase the performance of Indexing Service queries
Annealing merge:
Combines shadow indexes into fewer shadow indexes and takes place when the server is idle and necessary server resources are available
Master merge:
Combines shadow indexes with an old master index (if present) to create a new master index