DB2 Design Considerations

1. Placement of change columns should be close together on the row
-UNDO/REDO records are formatted from 1st column of change to last column of change for fixed length rows
-UNDO/REDO records are formatted from 1st column of change to end of row for variable length rows (rows with VARCHAR columns) when NO VARCHAR columns are changed
-entire row is formatted for variable length rows when VARCHAR columns are changed
-UNDO/REDO records are the before and after image of the changed columns needed for recovery
-the larger the UNDO/REDO records are the more I/O is required to write to the active logs
-if by chance the active logs are being fill faster than the system can archive the logs to tape and NO active logs is available, the DB2 subsystem STOPS until an active logs gets archived (tape drive problems could also create the same problems)