The purpose of an index rebuild, PROUTIL IDXBUILD, is to increase index efficiency and to correct errors. Use this utility when index corruption forces a rebuild of an index or when you can take your database offline for index maintenance. Your database must be offline when the index rebuild utility is run. You can use a combination of online utilities, including index fix and index compact, to approximate the effect of an index rebuild.
You will get significantly better organization within the indexes by sorting them prior to merging them back into the database. You can do this by opting to sort when running the index rebuild. Be aware that sorting requires substantial disk space (50 to 75 percent of the entire database size when choosing all indexes).
You cannot choose a level of compression with index rebuild. The utility tries to make indexes as tight as possible. While high compression is good for static tables, dynamic tables tend to experience a significant number of index splits right after an index rebuild runs. This affects the performance of updates to the table. Even with the decrease in update performance, the overall benefit of this utility is desirable. The performance hit is limited in duration, and the rebuild reduces I/O operations and decreases scatter of the indexes.
