Example of a badly organized database

Processing a badly-organized database in logical-record sequence typically results in an I/O reference pattern that accesses many DASD blocks in a random sequence.

This happens because many segments were stored in randomly scattered blocks after the database was loaded or reorganized. When your database is accessed in a predominantly random pattern, most I/O operations issued by the SB buffer handler are random reads. SB is not able to issue many sequential reads, and the elapsed time for your job is not considerably reduced.

You can use the SB buffering statistics in the optional //DFSSTAT reports to see if your database is well-organized. Your database is likely to be badly organized if a large percentage of the blocks were read with random reads during sequential processing. You can monitor this percentage over a period of time to see if it increases as the database ages.