Indexing Service is no longer supported as of Windows XP and is unavailable for use as of Windows 8. Instead, use Windows Search for client side search and Microsoft Search Server Express for server side search.
The MasterMergeCheckpointInterval entry is the amount of information indexed before Indexing Service generates a checkpoint for a master merge.
|Range:||256 - 4096|
The value of the MasterMergeCheckpointInterval entry determines how much work (data written to the new master index) needs to be redone if a master merge is paused and restarted.