Several data utilities are provided. It is good practice to backup before performing any data utility.
Upgrade is a routine operation performed after you have installed a new version of the program. It makes any changes that may be necessary in the data base structures because of changes in the program.
Pack Data removes the space taken by deleted records from your files. It is good practice to Pack periodically.
Resave checks to be sure that data stored in more than one file is the same in both places.
Reindex repairs the index files for your data.
Clear Prpro empties the file that stores images of your prayer cards, etc. It does not empty the underlying data so it is possible to remake the cards if you know what verse was used. If you print pictures on your cards, the image file can become big quickly and that can cause problems. If you aren't experiencing problems, it is probably sufficient to choose to Pack the Data rather than Clear this one file.
Copy Empty Data starts you over again completely by copying a backup set of empty files over your data. You wouldn't do this normally unless you had some play data which you wanted to delete or you were getting ready to convert redundant data from another program. Create Empty Data refreshes the backup set of empty files to be sure it is in the latest format.