A Vision version 4 file is about 5 GB total size with 37 million records.  It has two keys and there is a need to specify an existing field as another key.  A COBOL program was created to read the existing file and write to the new file.  That program executed very slowly.  It had not finished after running for over a day.  The file is used for a batch process that must run every day so a faster method is needed.

The vutil -unload and -load options will produce much faster results in moving the data from the old file to the new file. 

First, unload the data into a binary sequential file using:

     vutil -unload -b originalfile tempfile

Next create the new empty file with an OPEN OUTPUT from a COBOL program. 

Next, after you have an empty file with the new definition load the data with:

     vutil -load -b temptfile newfile

Lastly rename the newfile with the original file name.