DEDB space search algorithm

The DEDB space search algorithm attempts to store the data in the minimum amount of CIs rather than scatter database record segments across a greater number of RAP and overflow CIs.

This topic contains Diagnosis, Modification, and Tuning information.

The trade-off is improved performance for future database record access versus optimum space utilization.

The general rule for inserting a segment into a DEDB is the same as it is for an HD database. The rule is to store the segment (root and direct dependents) into the most desirable block.

For root segments, the most desirable block is the RAP CI. For direct dependents, the most desirable block is the root CI. When space for storing either roots or direct dependents is not available in the most desirable block, the DEDB insert algorithm (described next) searches for additional space. Space to store a segment could exist:

• In the dependent overflow
• In an independent overflow CI currently owned by this UOW

Additional independent overflow CIs would be allocated if required.