HD databases do a Format Logical Cylinder, so always allocate on full cylinder boundaries. Keep segments to be accessed in the same block as the entry segment. FREESPACE should be large enough to insert the largest segment type, including its prefix. Code large block sizes, such as 18 K or 26 K. Code SCAN=0. Code pointer of Twin-Backward or No-Twin on the root (reduces lock conflicts on inserts). If you are coding FREESPACE, code free blocks and use the second-most desirable block, code SEARCHA=2. Unsequenced Segments: ­ Use insert rules as follows: · · (,FIRST) (,LAST) with Physical Child Last pointer ­ Sequence segments only if required. ­ Use "9s complement" if adding higher keys. Different data set groups have separate bitmaps. Therefore, if there are long segments in the database, by using different data set groups, you are able to insert the smaller segments if space was available. A.6 OSAM