Segment placing with load control

The normal space search algorithm places segments into the control intervals in a tightly packed manner.

The root segment is placed within the RAA block (if room is available) that is determined by the randomizer. Direct dependent segments belonging to the root are placed into the same RAA block or DOVF blocks within the UOW until they are all used. IOVF blocks are selected and filled as needed.

Placement of segments within the types of control intervals (RAA, DOVF, and IOVF) has a significant impact on performance. Consequently, it is sometimes useful to influence the space search algorithm during the reorganization function to relegate infrequently used segments into IOVF (or DOVF) blocks. Segment placement will preserve space in the RAA (or DOVF) blocks for more active data.

Placement of selected segments during the reorganization function can be accomplished by using the LOADCTL subcommand and its related keywords. The LOADCTL subcommand lets you control segment placement in the following ways:

  • Select a segment, a segment and its dependents, or its dependents only for placement

  • Control the placement of selected segments into IOVF or DOVF

  • Control placement of segments, based on their data content

  • Control placement of segments, based on a specified number of segment occurrences

Note

To maintain this data placement, you must continue to use the same LOADCTL subcommand (or subcommands) for any subsequent reorganization processing on the DEDB.

The following figure shows a typical DEDB hierarchy. This hierarchy is used in subsequent examples in this section that show how the LOADCTL subcommand can be used with its associated keywords.

Database hierarchical structure in LOADCTL examples


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