Record Padding option

Such increases can occur when information is added to the record during updates or when the changed information does not compress as well as the information it replaces. When you use the Record Padding option, you must be very familiar with the size of the records in your data sets and how the size changes over time.

When you use the Record Padding option, compression routines place a specified amount of empty space in the records before inserting the records into the data set. As you update these records, DATA ACCELERATOR Compression uses the empty space when the compressed record increases in length. When the compressed record decreases, the actual length of the record is not changed; there is just more empty space in the record because of the record pad. Padded records can grow larger than their original padded size, but cannot decrease in size from the original inserted length until the data set is reloaded or until you turn off the Record Padding option.

The following figure illustrates the pad relationships.

If you load your data set originally with a small amount of data and you know that much more data will be placed into the records during updates, you can specify a pad when the data set is originally loaded. During update, you can turn the Record Padding option off (without reloading the data set), to allow access by records that need to use the space, but allow the pad to be eliminated from records that do not need it.

The expected record growth in a data set determines the amount and type of record padding that should be used. Use padding appropriately. Too much record padding might jeopardize the benefit of compressing the data set.