As the index file grows, logically adjacent portions of the index file, termed nodes, are liable to be widely separated on the disk. This fragmentation of the index reduces the performance of programs using the database. To check how much fragmentation has occurred to the index file, you can use the database integrity checking utility and see whether the node number displayed increases steadily or moves up and down erratically.
The optimise index file option rearranges the index so that the index nodes are in the most efficient order for searches. To use this option your system must have enough disk space to write another copy of the index file. The old index is not deleted until the process is completed. This option of REORGDB does not usually take very long to run.
All the options that build an index file call this option automatically, unless the -FAST option was specified.
On the Database Reorganisation menu, select option 4 - Optimise index file. DP4 optimises the index file. It displays the number of index nodes to process and the number processed so far
When the reorganisation utility terminates, press <Enter> to return to the DP4 System menu
A machine crash while this option is running does not harm the database. If one happens, just optimise the index again.