Index Size

Index size is a function of index field width, the number of different index values that occur in the report, and how the report is sorted. Sorting affects index size because each index entry contains a separate pair of pointers to the first and last page of each nonconsecutive occurrence of the index value in the report. The indexes in an index path are shorter when the report is sorted by the fields which comprise the index path.

For example, a bank report may contain information about 10,000 accounts divided among 10 account types at 50 branches. If the report is sorted by branch #, account type, and account #, the account type index would have only 10 entries but each entry could point to as many as 50 page ranges. If the same report were sorted by account type, branch #, and account #, the account type index would still have 10 entries but each entry would point to only one page range containing all the branch # values per account type entry.