Advantage of SYNC Class

The SYNCHRONIZED clause is sometimes used with USAGE IS COMP or USAGE IS INDEX items. It is used to optimize speed of processing but it does so at the expense of increased storage requirements.
The word SYNC can be used instead of SYNCHRONIZED.
The SYNCHRONIZED clause is used to explicitly align COMP and INDEX items along their natural word boundaries. Without the SYNCHRONIZED clause, data-items are aligned on byte boundaries.
Example: 01 TWO-BYTE PIC S9(4) COMP SYNC.