DB2 9 & 10 for z/OS Overview

Migration Planning WorkshopAdditional Non-key Columns In An Index• Indexes are used to enforce uniqueness constraints on tables• To achieve index only access on columns not part of the unique constraint,additional indexes are often created for the non-unique columns– Slower DB2 transaction time– Increased storage requirements• In DB2 10 Additional Non-key Columns can be defined in a unique index toreduce total amount of needed indexes• Indexes that participate in referential integrity (RI) will support additionalcolumns, but INCLUDE(d) columns will not be used to enforce RI• Improves:– insert performance as less indexes need to be updated– space usage– Can stabilize access path as optimizer has fewer similar indexes to choosefrom166© 2011 IBM Corporation